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SHOP SKETCHING 



McGraw-Hill DookCotrtpaiiy 

Pu66^s/iers of3oo£s/b7' 

Electrical World TheLngineGiin^ and Mining Journal 
tngiriGGring Record Engineering News 

Railway Age Gazette American Machinist 

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Electric Railway Journal Coal Age 

>fe>tallurgical and Chemical Engineeiing P o we r 



IXDLSTRI.\L EDUCATION SERIES 

SHOP SKETCHING 

PREPARED IX THE 

EXTEXSIOX DIYISIOX OF 
THE rXITERSITY OF WISCONSIN 



BY 

JOSEPH W. WOOLLEY, B. S. 

AND 

ROY B. MEREDITH, B. S. 

SOMETIME IXSTRUCTOBS IX MECHAXICAL EXGIXEERIXG IX THE 
rXIVERSITY EXTEXSIOX DIVISIOX 



FIRST EDITION 



McGRAW-HHL BOOK COMPANY, Inc. 
239 WEST 39TH STREET. NEW YORK 

6 BOUVERIE STREET, LONDON, E. C. 
1913 



Copyright, 1913, by the 
McGraw-Hill Book Company, Inc. 



THE. MAPLK. PRESS. YORK. I* A 



^/ 



a~o 



■GI.A3582J0 



T353 

.\A)85 



PREFACE 

This volume presents the instruction papers prepared and used 
by the University Extension Division as a course for apprentices 
and older shop men who need a knowledge of mechanical drawing. 
The method of instruction is founded on those basic laws of suc- 
cessful vocational instruction: that the instruction must give 
the man just what he is going to use in his everyday work, and 
that this must be given in the most direct and efficient manner 
with the least expenditure of his time and money. 

Every good mechanic must have a knowledge of drawing for 
two reasons. First and most important, he must be able to read 
mechanical drawings ; the lines on a blueprint must not be merely 
so many white lines on a blue background, but they must delin- 
eate an actual object in his mind. In other words, he must be 
taught to visualize the object from the drawing. Second, he 
must be able to make such occasional sketches as the better 
mechanics are often called upon to make. He may be on a repair 
job which requires that a sketch be made of a broken part; or 
he may want to convey to another his ideas of a special tool or 
fixture or machine part. At times he may find it necessary to 
make a pictorial representation for the benefit of someone who 
can not understand a regular drawing. In making dra^\angs 
for any of these reasons, he would use only the simplest outfit — 
a pencil, a piece of plain paper (often a scrap of wrapping paper of 
the back of an envelope), a scale or ruler for a straight-edge, and 
possibly a pencil compass. 

This text is not intended to make draftsmen, but to teach shop 
men the knowledge of drawing that they need as shop men. 
Ability to read drawings is developed by examples from simple 
and well-known objects. This is further brought out and tested 
by problems requiring the student to construct other views from 
given drawings. To do this he must be able to visualize the 
thing represented and at the same time he is taught to make 
simple sketches. Other problems give practice in sketching 
from actual objects. 

No attempt has been made to establish a standard of conven- 
tions. Those more generally accepted are given and, while sug- 

V 



vi PREFACE 

gestions are made for the unattached student, it is expected that 
each shop man will use those that are accepted in his own shop. 
Experience has shown that mechanics frequently resort to a pic- 
torial method of representation, especially in conveying ideas 
to those unfamiliar with mechanical drawings. The isometric 
method has therefore been introduced, believing that it is in 
general the simplest of the oblique methods of representation. 
Freehand work, while desirable, introduces an added complica- 
tion to the instruction and has therefore been left until the last. 

The student should not be taught to depend on the use of 
drawing instruments which are not available '^ on the job." 
The following simple outfit is suggested: A pad of large size 
letter paper with a hard, unruled surface; a 2-H pencil; a steel 
scale or a folding rule; an eraser; and a pencil compass such as 
the Eagle Pencil Go's. No. 569. When a student shows marked 
ability and interest he may be encouraged to use a regular 
drafting outfit and to do ink work and tracing if he desires to 
spend the extra time required. 

The course was originally written by Mr. Woolley and was 
later revised by Mr. Meredith, who incorporated such additions 
and changes as his experience in teaching it to several classes 
of shop men showed to be desirable. The illustrations were 
drawn by Mr. Ralph W. Hills, Instructor in Mechanical Drawing 
in the Extension Division. Mr. Hills has also contributed mam- 
valuable suggestions in the development of the course. 

Earle B. Norris, 

Associate Professor of 

Mechanical Engineering. 
The University of Wisconsin 
Madison, Wisconsin. 
October 1, 1913. 



CONTENTS 

Peeface vii 

CHAPTER I 
Principles of Mechanical Drawing 

Art. Page 

1. Projections 1 

2. Relations between views . . . / 4 

3. Making the drawing 5 

4. Dimensioning the drawing 6 

5. Order of procedure 10 

6. Broken lines 13 

7. The compass 20 

8. Arrangement of dimensions 21 

9. Finish 22 

10. Drawing to scale 22 

11. Finish marks 23 

12. Fillets 25 

13. Notes on dimensioning 26 

14. Drawing from objects 28 

CHAPTER II 

Screws and Screw Fastenings 

15. The nominal or outside diameter 31 

16. The root or effective diameter 31 

17. Depth of thread 31 

18. Forms of threads 31 

19. The V thread 31 

20. The U. S. standard thread 32 

21. The square thread 32 

22. The Acme thread 32 

23. The worm thread (B. & S. standard) 32 

24. The Whitworth thread 33 

25. Pitch 33 

26. Bolts 33 

vii 



viii CONTENTS 

Art. Page 

27. Bolt heads and nuts 35 

28. Thread conventions 36 

29. Right-hand and left-hand threads 36 

30. Tapped holes. 37 

31. Other thread conventions 39 

32. Method of drawing square threads 39 

33. Cap screws 40 

34. Machine screws 41 

35. Set screws 41 

36. Multiple threads , / 43 

37. Lead 43 

CHAPTER* III 

Sections 

38. The use of sections . 45 

39. Half sections 46 

40. Broken sections 48 

41. Partial sections 50 

42. Revolved sections 50 

43. Shortened views • 53 

44. Assembly drawings in section 56 

45. Conventions for cross-hatching 58 

46. Conventions for pencil work 62 

CHAPTER IV 

Assembly and Detail Drawings 

47. Assembly and detail sheets 63 

48. Drafting-room procedure 68 

CHAPTER V 

Gearing 

49. Spur gears 70 

50. Bevel gears 71 

51. Spiral and worm gears 71 

52. Pitch circles 71 

53. Pitch diameter 72 

54. Pitch 72 



CONTENTS ix 

Art. Page 

55. Gear calculations 73 

56. The addendum 74 

57. The dedundum 74 

58. Gear repairs 75 

59. Gear drawings 75 

CHAPTER VI 

Isometric Drawing 

60. Pictorial drawing 79 

61. Isometric axes 80 

62. Circles in isometric ^ , 82 

63. Oblique surfaces in isometric 83 

64. Examples of isometric drawing 86 

65. Isometric paper 88 

66. Isometric drawing on plain paper 92 

CHAPTER Vn 
Freehand Drawing 

67. The use of sketching paper 95 

68. Sketching on plain paper 97 

69. Freehand isometric sketching 99 

Index. 101 



I 



viii CONTENTS 

Art. Page 

27. Bolt heads and nuts 35 

28. Thread conventions 36 

29. Right-hand and left-hand threads 36 

30. Tapped holes. 37 

31. Other thread conventions 39 

32. Method of drawing square threads 39 

33. Cap screws 40 

34. Machine screws 41 

35. Set screws 41 

36. Multiple threads , . ^ 43 

37. Lead 43 

CHAPTER* III 

Sections 

38. The use of sections 45 

39. Half sections 46 

40. Broken sections 48 

41. Partial sections 50 

42. Revolved sections 50 

43. Shortened views • 53 

44. Assembly drawings in section 56 

45. Conventions for cross-hatching 58 

46. Conventions for pencil work 62 

CHAPTER IV 

Assembly and Detail Drawings 

47. Assembly and detail sheets . 63 

48. Drafting-room procedure 68 

CHAPTER V 

Gearing 

49. Spur gears 70 

50. Bevel gears 71 

51. Spiral and worm gears 71 

52. Pitch circles 71 

53. Pitch diameter 72 

54. Pitch 72 



CONTENTS ix 

Art. Page 

55. Gear calculations" 73 

56. The addendum 74 

57. The dedundum 74 

58. Gear repairs 75 

59. Gear drawings 75 

CHAPTER VI 

Isometric Drawing 

60. Pictorial drawing 79 

61. Isometric axes 80 

62. Circles in isometric ^ , 82 

63. Oblique surfaces in isometric 83 

64. Examples of isometric drawing 86 

65. Isometric paper 88 

66. Isometric drawing on plain paper 92 

CHAPTER VII 
Freehand Drawing 

67. The use of sketching paper 95 

68. Sketching on plain paper 97 

69. Freehand isometric sketching 99 

Index 101 



SHOP SKETCHING 

CHAPTER I 

PRJNCIPLKS OF MECHANICAL DRAWING 
ASSIGNMENT 1 

1. Projections. — The principle of projections is the basis of 
mechanical drawing and must be thoroughly understood in order 
to read a mechanical drawing or to make one. 

In making a mechanical drawing of any object, a draftsman 
deals with one face at a time, and makes separate drawings or 
views showing how the different sides or faces look. Thus we 
sometimes make as many different drawings or views of an object 
as the piece has different sides. Each view is made as if the 




Fig. 1. 

draftsman w(;re looking squarely at tlic particular side he is 
drawing. In Fig. 1 is shown a picture of an oilstone, such as 
might be made by an artist or a photographer. Looking to- 
ward the corner, as in this figure, we see three faces, the side A, 
the end C, and the top B. Fig. 2 shows a mechanical drawing 
of this same oilstone. Notice that the stone has its three different 
faces shown by the three views A, B, and C. In all there are 
six faces but, since the two ends are alike, and likewise the two 

1 



2 SHOP SKETCHING 

sides, and the top and bottom, it is necessary to show only the 
three different faces. Each view is a picture of one side as we 















B 






X 








A 


— Y 


C 















Fig. 2. 




Fig. 3. 



would see it if the stone were held squarely in front of, and on a 
level with the eye. 
In making these views showing the different sides of any 



PRINCIPLES OF MECHANICAL DRAWING 3 

object, they should be placed in such a way as to show how they 
are related to each other in their position on the object. This is 
done by the principle of projection as follows: Referring to 
Fig. 2, notice that the top view B is placed directly above the 
side view A, so that the edges of B are on the same line as those 
of ^, as shown by the dotted lines. Also, end view C is directly 
in line with A. This is the principle of projection. In other 
words, the length of A is ''projected" directly upward to form 
the length of B and the height of A is ''projected'^ to the right 
to form the height of C. The dotted lines are never actually 



2 



Left End 
Elevattiom 




Side Elevation 



-W 



C] 



2 



B 



V^ 



RiQMT End 
Elevation 



Bottom Vietw. 



Ftg. 4. 



drawn, but simply indicate the position of the straight edge in 
laying out the work. 

Fig. 3 shows a picture of an anvil. Fig. 4 shows the complete 
mechanical drawing of this anvil with the correct names of the 
different possible views that might be shown. As a general rule, 
we follow this grouping: In the center we place the side view 
which shows the object set up in its natural position before the 
eye, and project the other views from it, placing the plan or top 
view above, the bottom view below, the right-end view or eleva- 
tion on the right, and the left-end view on the left. 



SHOP SKETCHING 



The views of an object which show it set up before the eye in 
its natural position are called elevations and are further desig- 
nated as front, side, or end elevations. The top view, obtained 
by looking down upon an object is usually called the plan. The 
names which we give to the elevation views differ with different 
objects and different people. Usually we have two elevations 
given in a mechanical drawing, but people look at things differ- 
ently and the view that some people would call a front view 
others might consider a side view. So we might have front and 
side elevations, or front and end elevations, or in the case of 
any object that does not have any particular face that could 
be called the front, we might call the elevations the end and side 
elevations. 

Note Carefully. — We seldom need more than two or three 
views of a piece in order to show it. Generally a plan and side 
and end elevations are all that is necessary. It is only with 
very irregular objects like the anvil that we need as many as 
five views. 



2. Relations Between Views. 



-Fig. 5 shows a sketch in one 





Tenon. 



Mortise 



Fig. 5. 



view of two blocks of wood which are formed so that they may 
be j oined together with a mortise-and-tenon j oint . A mechanical 
drawing of the tenon is shown in Fig. 6. Three views are shown, 
namely, the side elevation AB, the plan CD, and the left-end 
view EF. The left-end view is shown rather than the right-end 



PRINCIPLES OF MECHANICAL DRAWING 5 

view because the form of the block and also of the tenon are shown 
in the left-end view. The surface A in the side elevation is shown 
in the other two views by the lines a. The surface B in the side 
elevation is represented by the lines h in the other two views. 
The student should check over the rest of the drawing with the 
aid of the letters so as to see just what each line in one view 
represents in the other views. The capital letters are used to 
mark the surfaces. The small letters mark the lines which in 
other views represent these same surfaces. These letters are 
shown merely by way of explanation and would not appear upon 
a working drawing. From this drawing it will be seen that 
whenever a surface lies flat and on a 'level with the, eye, it is repre- 
sented by a line. 

3. Making the Drawing. — In making the drawing in Fig. 6, 



















^ 




f-^ 


D 




^A 




J= 










E 




^d 


A 




A 


B 



















Fig. 6. 



we would draw the side elevation (view AB) first, laying off the 
various dimensions with the scale. Then in drawing the plan 
view (view CD) we would use the principle of projections to 
simplify the work and to locate the view properly with respect 
to the side elevation. The vertical (up and down) lines on the 
side elevation we would extend or project upward with the 
straight edge. These lines would then show the lengths of the 



6 SHOP SKETCHING 

horizontal (cross\vise) lines of the top view. After deciding 
how much space to leave between the views, we would then draw 
the horizontal lines of this view, spacing them properly with the 
aid of the rule or scale, to show the desired width of the object. 
The left-end view is drawn in a similar manner, by extending 
toward the left the horizontal lines of the side elevation and 
locating the vertical lines with the aid of the rule. These lines 
which are drawn from the side elevation in determining the 
other two views are called projection lines. They are usually 
drawn lightly so that they may be readily erased from the finished 
drawing. The distance to be left between the views is largely a 
matter of choice. The considerations which govern it will be 
developed later. From the preceding discussion it will be seen 
that the following relations exist between the different views: 

The horizontal dimensions of the side elevation and of 
the plan or top view are equal. 

The vertical dimensions of the side and end elevations are 
equal. 

The horizontal dimensions of the end view and the 
vertical dimensions of the top view are equal. 
4. Dimensioning the Drawing. — After the representation of 
the object is completed, it must be dimensioned for the guidance 
of the mechanics who are to have a part in its manufacture. 
Fig. 7 shows a shop drawing of the tenon shown in Fig. 5. It 
will be noticed that the extension lines and dimension lines have 
been added. 

Dimension lines are light lines broken at the center for the 
insertion of the dimensions, and having arrowheads at their 
ends to show the distances which they measure. The arrowheads 
should be made very sharp. As shown in Fig. 8, they should 
have a sharp wedge shape with a slight curve to the sides rather 
than a V-shape. They should not be blocked in solidly. 

Extension lines are light lines which show the points on the 
object between which the dimension is measured. Extension 
lines should be drawn up to about iV in. from the object and 
should project about | in. beyond the dimension lines. 

Dimension lines should be spaced equally apart and equally 
distant from the object lines. About i\ in. is a good average for 
this spacing. Dimensions should be placed in one or two views 
when possible. Notice in Fig. 7 that all the dimensions are 
shown in two views. It is bad practice to repeat dimensions — that 



PRINCIPLES OF MECHANICAL DRAWING 



is, to put the same dimension in more than one of the views. Dimen- 
sions which are closely related should be placed near to each 
other, as shown by the arrangement of dimensions in the left- 



|5" 

I5 



4l" 



1 



'8 






-1^ 



Detail, of Tenon 

FOR 



Mortise and Tenom Joint. 



Fig. 7. 

end view of Fig. 7. The dimension 4f in. is known as the over-all 
dimension. It is usually given so that the workman may 
know the total length of material required. The over-all dimen- 



AVOID 




CORRECT 



Fig. 8. 

sion should be placed just outside the dimensions of which it is 
the sum, so that its dimension line will not be cut by any extension 
lines. Be sure that your small dimensions add up to be the 
same as the over-all dimension. 



8 SHOP SKETCHING 

Dimensions are usually shown by vertical figures about | in. 
high. Fig. 9 shows the type of numerals generally used. The 
total height of fractions should equal twice the height of the 
whole numbers. The dividing line of a fraction should be oppo- 
site the middle of the whole number and should be on a level with 

Freehand Lettering 

ABCDEF6HIJKLMN0PQRSTUVWXYZ& 
'^^^ 'B^ \l [B V 12 345 678 90 

ABCDEFGHIJKLnNOPQR5TUVWXYZ& 

I234567890 ^f 3| 7^ 
Fig. 9. 

the dimension line. The figures of the fraction should not 
touch the dividing line. All horizontal dimensions should read 
from the bottom of the sheet, and all vertical dimensions from the 
right-hand side of the sheet. Notice Figs. 11, 13, and 15, in this 




Fig. 10. 

respect. In all of the dimension lines that run up and down the 
sheet the dimensions are placed so that they can be read from 
the right-hand end of the sheet. 

In Fig. 10 is shown a picture of two pieces that form an end 
lap joint. A mechanical drawing of one of the pieces is shown 



PRINCIPLES OF MECHANICAL DRAWING 



9 



in Fig. 11. Fig. 12 shows a cornerwise picture of an angle brace. 
Fig. 13 shows a complete shop drawing of the same angle. These 




Fig. 11. 




Fig. 12. 

drawings should be studied carefully observing the following 
points: . 



10 



SHOP SKETCHING 



Relative positions of the views. 

Relations between lines in the different views. 

Arrangement and position of dimensions. 

Extension lines and arrowheads. 
5. Order of Procedure.— In making a drawing, the first thing 
is to select the views to be shown and then plan their arrange- 
ment so that they will look well balanced on the sheet. If the 
left-end view is to be shown, the side elevation should be placed 
to the right to leave room for it; if the right-end view is shown, 
the side elevation should be placed to the left of the center. If 









































2 












' 






rt 


1 










i 










' 




-KVJ 












-»'• 




t 




-.4" - 










f-t 






* 




1 


1 




Ancsle 










4-REQUlRED STEEL 




JOHN JONES 
8-30-f9l2. 



Fig. 13. 



both ends are shown (which is only when they are very different) , 
then the side elevation would be placed about in the center. The 
elevations should be placed enough below the center of the 
space so as to leave room for the top view, if it is to be shown. 

The lines of the object should then be drawn, probably con- 
structing the front or side elevation first and then constructing 
the other views by the aid of projections from this view. 

After the representation of the object is complete, the extension 
and dimension lines should be drawn, making them lighter than 
the object lines; next, the arrowheads should be put on; and then 



PRINCIPLES OF MECHANICAL DRAWING 11 



the dimensions should be shown in vertical numerals about 
high and similar in form to those shown in Fig. 9. 



in. 




Fia. 14. 



Finally, every plate should contain a title, which should show 
the name of the object, the number of pieces required for the 





k!-"-* 




u-5':^ 






z. 




s 
















^ , 










V^ 




' 




„ 










* 


A— »r 












^z *^ 






Kev 








I-REQUIRED MACh. STEEL 








FINISH ALL OVER 







Fig. 15. 



machine on which it goes, the material of which they are to be 
made, and the scale of the drawing. There should also appear, 



12 SHOP SKETCHING 

usually in one corner, the name of the draftsman and the date 
when the drawing was made. The plain vertical capitals shown 
in Fig. 9 are preferred for titles and notes as they are easily made, 
are very legible, and require the least practice to do a presentable 
job. The name of the object, being the most important part of 
the title, should be put in large letters, about i\ in. high. All 
other lettering on the plate should be about J in. high. In order 
to get the lettering on a straight line, very light guide lines 
should be drawn before beginning to letter. 

As the mechanic is guided in his work by information which is 
given entirely on the drawings, it is, therefore, necessary that all 
drawings should give complete information. Besides showing 
the shape and size of the parts, the drawings must give full 
information as to the material to be used, the finish of all surfaces 
— whether rough, machined, tempered, hardened, etc.^ — ^the 
kinds and sizes of all screws, bolts, etc., and the number of pieces 
required. 

PROBLEM 1 

Fig. 14 shows a sketch of a gib key. A working drawing of this key is 
shown in Fig. 15, with an appropriate title. Such a key is used for fasten- 




FiG. 16. 

ing pulleys, couplings, or collars to shafts and is driven into a slot, half of 
which is cut in the shaft and half in the piece to be fastened to the shaft. 
The head is used for pulling the key out of the slot. The slots cut in the 
shaft and pulleys are called ''key ways." 

Fig. 16 shows the same key as was shown in Figs. 14 and 15, when viewed 
from a different position. 

Make a working drawing of this gib key, making the views the full size 
of the key according to the dimensions given in Fig. 15. Draw the views 



PRINCIPLES OF MECHANICAL DRAWING 13 

of the key that would be obtained by looking along the arrows, C, D, and E, 
in Fig. 16. The arrangement of the views should be as shown in Fig. 17. 
Use the scale or rule for pointing off dimensions, and also as a straight-edge 
for drawing the lines. Dimension the drawing and show a complete title 
beneath the drawing, with your name and the date in the lower right-hand 
corner of the plate. 

Before starting any drawing, always see that your pencil is properly 
sharpened to a good point. Good clean lines cannot be made with a duU 
pencil. 



DRAW PLAN VIEW MERE 



DRANA/ END 
VIEW HERE 



Fig. 17. 



ASSIGNMENT 2 



6. Broken Lines. — In drawing any view, if a surface is hidden 
from sight but needs to be shown in some manner, it is customary 
to use a broken line. This hne will show the location and extent 
of the hidden surface, but, by being broken, will indicate that 
the surface represented is not on the front but is out of sight. 

Broken lines are drawn with dashes about | in. long with 
spaces about -3V in. long between them. See Fig. 31. In drawing 
broken lines, they are usually made just a little lighter than the 
full object lines of the drawing. ' 

In Fig. 13, the angle was represented by solid lines throughout, 
because, in the views selected all the surfaces represented were 



14 



SHOP SKETCHING 



^^ I ,3L 



Fig. 18. 




Fig. 19. 



PRINCIPLES OF MECHANICAL DRAWING 



15 



visible. If, however, we wash to show the right-end view, it 
will appear as shown in Fig 18; the surface a is shown in the 
right-end view by the broken line a\ because the surface a is 
concealed from the eye by the upright leg of the angle. The 
right-end view of Fig. 11 would appear as in Fig. 19, and the 
right-end view of Fig. 7 would appear as in Fig. 20, for the 
same reasons. Hidden surfaces must always he shown by broken 
lines. The student should practise making broken lines so that 
he can space them uniformly by eye. 

A judicious selection of the views to be shown will often avoid 



I -» 

I I 
I I 

I I 



Fia. 20. 



the necessity of using broken lines. For example, the left-end view 
of Fig. 20 shows the end outline of the tenon in full view and 
therefore is preferable to the right-end view. Figs. 21 and 22 
show a case where the broken lines are needed. These figures 
show a picture and a mechanical drawing of a bronze bushing. 
This is a hollow cylinder, the hole extending clear through from 
end to end. In the side view of Fig. 22 it is necessary to represent 
the hole by two broken lines. These lines extend throughout 
the length of the side view and thus indicate that the hole 
extends from one end of the piece to the other. Without these 



it) 



SHOP SKETCHING 



lines we could not tell how far the hole extended. These lines 
are located by projecting the top points of the inner circle of the 
end view. 




Fig. 21. 




3i' 



Bronze Bushing 
finish all over 



Fig. 22. 



Suppose now that we were to make a cylinder like that of 
Fig. 22 but closed at one end so that it would look like a cap for a 
pipe. It might then be shown by the side elevation and left-end 



PRINCIPLES OF MECHANICAL DRAWING 



17 



view of Fig. 23. Notice how the broken outline in the side 
elevation shows the form cf the interior and indicates that the 
hole does not extend all the way through the piece. These two 
views would be sufficient to give a clear idea of the cap. If the 
right-end view were desired, it would appear as shown at the 
right. The inner circle of this view is broken, because it repre- 
sents a hidden surface. 

Fig. 24 shows a ''stop" such as is commonly used on planer 
beds for bracing castings. It is shown by four views in Fig. 25. 
These views are not all needed but are given to show how the 



1 






/^ y''^ 


~" "^ ^v 




^^ 




1 
1 


/ 


\ \ 


11 


J 




1 
1 


1 \ 


1 
/ / 


\^ 


[^ 





1 


\v // 


• 


1 








r 



Fig. 23. 



stop would appear in the different views. The right-end view 
contains a broken circle, because the surface which it represents 
is concealed when the stop is viewed from the right end. The 
side elevation and left-end view are all the views needed to give 
a complete idea of the shape of this stop. 

Fig. 26 shows a sketch of a flange bushing. A complete shop 
drawing of this flange bushing is shown in Fig. 27. When the 
bushing is viewed from the left end, the 2-in. cylindrical surface 
is concealed from sight by the flange and is therefore shown by a 
broken line in the left-end view. 



18 



SHOP SKETCHING 



Always end a broken line with a dash running right up to the 
point where the surface ends which the line represents. Compare 




Fig. 24. 




































— 




/^ 


^, 








^ 


■^N 






f 


\ 










/ 


\ 




— 


\r 


y 










1 


1 












\ 
\ 


1 

/ 






^^r^ 










"t 




















1 




* 



Fig. 25. 



the ends of the lines in Figs. 28 and 29. Whenever a broken line 
crosses a full line, always make one of the dashes definitely 
cross the full line. The correct method of observing this is 



PRINCIPLES OF MECHANICAL DRAWING 



19 



also shown in Fig. 28, and the improper method is shown in 
Fig. 29. 

If the bushing is shown on a shaft, the diameter of which is 




Fig. 26. 



the same as that of the hole, then the broken lines will terminate 
as shown in Fig. 30. This explanation applies not only to this 
particular problem, but to all similar cases. 




I" 



nOQD 



CVJ 



Flange Bushing 
2 required brass 
finish all over 



Fig. 27 



In all work in drawing, full-line views should be shown rather 
than broken-line views. For instance, in drawing the cap of 



20 



SHOP SKETCHING 



Fig. 23, it is better practice to show the side elevation and left- 
end view rather than the side elevation and right-end view, 
because in the former case all of the lines of the end view are 
full lines while in the latter case one of the circles is broken. 

7. The Compass.— Circles are drawn by means of a compass. 
This consists of two legs hinged at the top; one leg contains the 
center point while the other contains the pencil point. In order 
to have all lines on the drawing of uniform weight and quality, 
it is well for the student to break some lead from his sketching 
pencil and insert it in the compass. The best results will be 
obtained if the lead in the compass is sharpened only from the 
outside, either with the knife or, better, by rubbing it on a 
smooth file, emery cloth, or sandpaper. Do not touch the 



CORRECT AND INCORRECT METHODS OF SHOWING BROKEN UNES. 




CORRECT 

Fig. 28. 



AVOID 

Fig. 29. 



CORRECT 

Fig. 30. 



inside. The point will then produce sharp lines and stand con- 
siderable usage without resharpening. 

Only enough pressure should be exerted on the compass to 
produce distinct, clean-cut lines. Some draftsmen become quite 
proficient at drawing circles freehand, but a compass is always 
a valuable part of a sketching outfit. 

It will be seen that light dot-and-dash lines are shown through 
the center of the views of Figs. 22, 23, 25, and 27. These are 
known as center lines. Whenever an object is symmetrical 
about a common center line (that is, just alike on both sides of 
the center line) it is customary to show the center line on the 
drawing. The most common method is to use a line made up 
of dashes about an inch long with dots between. Center lines 
should be drawn lightly. The horizontal and vertical center 
lines of all circular views should be shown. In starting a sketch, 
the center lines should always he the first lines drawn. 

In making a drawing like Fig. 22, the center lines would be 
drawn first, and the circular end view next. The side view may 



PRINCIPLES OF MECHANICAL DRAWING 21 

then be constructed with the aid of projection lines from the end 
view. The object Hnes of a drawing, whether full or broken, 
should be be heavier than the center, extension, and dimension 
lines, as shown in Fig. 31 . To obtain this result, the pencil should 
be sharpened carefully at the beginning of the work. This will 
enable the student to draw fine but distinct center lines. The 
object should then be drawn, making the lines heavier. After 
completing the views, the pencil should be sharpened again 
preparator}^ to drawing the extension and dimension lines, which 
should also be fine lines. 



Fui-L. Lines 



B ROK e: n Lines 



Extension Lines 



4^" 

^8 



Dimension Lines 



Center Limes 
Fig. 31. 

8. Arrangement of Dimensions. — Always dimension full-line 
views rather than broken-line views. Dimensions should be 
placed as close as possible to the place which they measure so as 
to avoid the use of unnecessarily long extension lines; for example, 
in Fig. 27, notice how the extension lines for the 2f -in. dimension 
are drawn to the side elevation rather than to the end view. 
Dimensions should always be carried outside of the views of the 
drawing when convenient, so that the drawing may be the 
more easily read. 

In Fig. 27, it will be noticed that the hole is dimensioned 
on the end view, in which it appears as a circle. This is done 
because to dimension it on the other view would necessitate di- 
mensioning from hidden Hnes, which is undesirable. Dimensions 
placed in this way should be put on a slant so as to avoid the 



22 



SHOP SKETCHING 



center lines. A single dimension should slope 45°; that is, half 
way between the horizontal and vertical center lines. Fig. 32 
shows how a number of dimensions would be arranged on a 
circular end view, the dimension lines being arranged so as to 
divide evenly the spaces between the center lines. 




Fig. 32. 

9. Finish. — In several of the drawings shown, there appear in 
the title the words ''Finish All Over." This indicates that all 
the surfaces are to be machined to the dimensions shown in the 
drawing. The piece must therefore come to the machinist with 
extra stock all over and on the inside so that he can machine it 
to size. If a piece is cast, the pattern-maker must allow for this 
in making the pattern; if forged, the blacksmith must leave the 
extra material in forging. Different shops may use different 
phrases, such as Finish, Finished, Finished All Over, Fin., or the 
letters F. A. 0. * 



PROBLEM 2 

Make a full size working drawing of the flange bushing shown in Figs. 26 
and 27, drawing the side elevation and right-end view. Careful attention 
must be given to all directions contained in articles 6 to 9, inclusive. 

ASSIGNMENT 3 

10. Drawing to Scale. — Both of the drawings made by the 
student thus far (Problems 1 and 2) have been mixde full size. In 



PRINCIPLES OF MECHANICAL DRAWING 23 

Problem 1, the key was 4^ in. long, and we drew the top and side 
views each 4+ in. long. Also we made the end view f in. wide, the 
full width of the ke3^ Each view was a full-sized representation 
of that side of the key. 

This method is all right for small pieces, but when we get large 
objects to draw we cannot, of course, draw them full size on an 
ordinary sheet of paper. Neither is it always desirable to get 
sheets of paper as large as the objects to be shown. To over- 
come this difficulty and at the same time to keep the various 
parts of a large piece in proportion, we draw them to scale. This 
means that all lengths are reduced in the same ratio when 
laid down on the paper. Thus, a dramng might be one-half, 
one-fourth, or one-eighth of the size of the actual object. Sup- 
pose we had to make a drawing of a casting whose over-all 
dimensions were 32 in. X27 in. X16 in. If we drew this one- 
quarter size, our drawing would be 8 in. X6f in. X4 in. The pro- 
portions would be exactly the same but the views look as if 
we were looking at the object at long range. The dimensions 
placed on the drawing would be the full-size dimensions of the 
object, since the dimensions are for the guidance of the workman 
in making the piece. 

The title of the drawing always tells to what scale the drawing 
has been made. The title may say: Scale — half size or scale — 
quarter size, or whatever the case may be. The reduction is 
also frequentty expressed by giving the number of 'inches per 
foot"; that is, the number of inches on the drawing sheet used to 
represent 1 ft. on the actual object. On a half -size drawing, an 
object 1 ft. long would occupy only 6 in. Consequently a 
half-size drawing would be marked Scale: 6 in. = 1 ft. On a 
quarter-size drawing, 3 in. would represent 1 ft. Hence the 
scale would be 3 in. = 1 ft. Likewise, an eighth-size drawing 
would be to the scale of 1^ in. = 1 ft., a sixteenth size would be 
f in. = 1 ft., and so on. 

Fig. 33 shows a rocker arm drawn to a scale of 6 in. = 1 ft., or 
one-half size. Notice particularly that the full size of the part is 
always given in the dimensions. No matter what scale you choose 
in dimensioning, always give the full size of the finished object. 
This drawing also illustrates several features that have not been 
explained before. 

11. Finish Marks. — This rocker arm is not to be finished 
all over, but onty on the faces and through the holes of the head 



24 



SHOP SKETCHING 



3 
4- 




/ 



3" 
■4." 




(0 



10 




'8 



l#P 






^< i V 



Rocker Arm 

I-REQUIRED CAST IRON 
SCALE 6"= r. 



Fig. 33. 



PRINCIPLES OF MECHANICAL DRAWING 25 

and the hub. When a flat surface, such as the faces of these 
ends, is to be finished, the general practice is to put a letter / 
across the line representing this surface. Some concerns use the 
capital F, others the abbreviation Fin., while still others put 
the whole word FINISH in capitals just outside of the line. The 
finish mark shown in Fig. 33 will be used in this course because 
it is in most general usage. If a student is employed in a shop 
having different standards, it is suggested that he learn them and 
use them throughout his work. Notice particularly that, when 
a surface is to be finished, the finish marks are not placed on the 
view where the surface is shown in plan, but rather on the view 
where it is represented by a line. Wherever these marks 
appear, the pattern-maker or blacksmith allows extra stock. 
About iV in. is allowed on small parts, so that, if the draftsman 
leaves off a finish mark where there should be one, it is the 
same as making an error of tV in. The finish marks indicate to 
the machinist what work is to be done by him on the object. 

When a hole in an object is to be machined, it is customary to 
indicate the process to be used by printing the word after the 
dimension of the hole. Thus in Fig. 33 we have J in. BORE and 
IJ in. BORE to indicate that the holes in the ends of the rocker 
arm are to be bored out to the given dimensions. In Fig. 34 is 
shown a hexagonal (six-sided) hole in a wrench. The word 
BROACH indicates that the hole is to be finished by the broach- 
ing process. The forging for the wrench must therefore be made 
so that this hole will be undersize, leaving material to be removed 
by the broach. Likewise, we find holes marked REAM, DRILL, 
or TAP, according to the operation to be used in finishing the 
hole. In a similar manner cylindrical parts that are to be 
finished by turning in a lathe have the word TURN after the 
dimension. 

12. Fillets. — In the views of Fig. 33 it will be noticed that the 
faces of the arm are rounded into the hub instead of leaving a 
sharp corner. A further examination of the figure shows that 
this is done wherever two surfaces meet, so that there will not 
be any sharp corners on the object when made, except where it 
is to be finished. These small curves or arcs on the drawing 
represent fillets. A Fillet is a small curve used to avoid sharp 
corners where two surfaces come together at abrupt angles. 
All unfinished corners should he rounded by fillets, so as to provide 
for the smooth flow of the metal when casting or forging and also 



26 SHOP SKETCHING 

for strength, as a crack will generally start in a sharp corner if 
the piece is overstrained. 

These fillets are dimensioned by giving the radius, as is done 
with any curve which is not a complete circle. 

13. Notes on Dimensioning. — There are several new features 
in connection with the dimensioning of this drawing in Fig. 33. 
A fillet is dimensioned by a line drawn from the curve to the 
center from which the arc was swung. The arrowhead appears 
only on the one end next to the curve. The note i in. R is put 
at the other end and in line with the arrow. If the dimension 
line had been long enough it might have been broken and the 
dimension put in the break, as was done in the f in. R on the head 
of the rocker arm. Notice that the distance between the 
center lines of the hub and head is given, rather than the over-all 
dimension. This is the important dimension and must be made 
accurate in machining. In the side view at the left, the faces of 
the head and hub must be located accurately with respect to 
each other. It would not do to locate these from the unfinished 
face of the arm, so they are located from the center line of the 
arm. The width of the head is given as f in. over-all, but, since 
it is symmetrical about the center line, it is understood that this 
means | in. on each side of the center line. 

This drawing shows several cases where the space between the 
extension lines is verj^ limited. This is especially true of the key- 
way cut through the hub. In giving the width of the key way 
there was space enough for the figures but not for the arrows, so 
we put the arrows outside, pointing inward. The depth of the 
keyway is still narrower. Here the arrows both point in, and the 
dimension is placed outside and in line with one of the arrows. 

PROBLEM 3 

Make a /2aZ/-stje drawing of the f-in. Hexagonal Box Wrench, shown in Fig. 
34. In this sketch, only the top and right-end views are shown. The 
student is to show the top, right-end, and side views. Draw the top and 
right-end views first, and from them draw the side view by means of the 
principles of projection. 

In making this drawing half-size, the student should draw each dimen- 
sion only half as large as it is on the finished object, but he should insert 
the actual dimensions of the finished object in their respective places on the 
drawings, as before noted. 

Order of work: Always start by laying out the center lines. Locate 
them so that there will be sufficient room between views and so that the 
three finished views will balance up well on the paper. It is always best to 



PRINCIPLES OF MECHANICAL DRAWING 



27 



di'aw the circles and the curved surfaces fii'st and then connect them with 
straight lines, as smoother joints will result. However, it is not practicable 
to do this in all cases. In this problem, start with the head of the wrench. 
The head of the wrench is formed to fit a hexagonal nut for a f-in. bolt 
and is therefore known as a f-in. wrench. The size of wrench is always 




a 



mlTj- 



9^ 



DRAW SIDE ELEVATION MERE, 



5 



= 1 



"•fll^Si 



foioo 






^- 



-2-- 



J Hexagonal. Box Wrench 

DROP FORGED- MACM. STEEL 
SCALE 3>'= l' 



Fig. 34. 

designated by the size of the bolt whose nut or head it will span, rather 
than by the size of opening of its jaws. The hexagon is a regular six-sided 
figure. All the sides of it are equal and are the same length as the radius 
of a circle which just passes through the corners. This fact is of use in 




Fig. 35. 



laying out the hexagon, as shown in Fig. 35. The width of the hexagon is 
given as 1\ in. To lay it out, we must calculate the distance between the 
opposite corners, this being the diameter of the construction circle. This 
distance is 1.155 times the width of the hexagon, 

1.155X11 = 1.444 



28 SHOP SKETCHING 

This is very close to l,^ in. For the purpose of making the drawing we 
can draw a light circle of this diameter or of ff-i^. radius; then, beginning 
where the circle cuts the horizontal center line and using the compass, we 
can divide the circle into 6 equal parts by stepping off the radius (f| in.) 
around the circle as shown in Fig. 35. By connecting the adjacent points 
thus found, we will have a hexagon approximately Ij in. across. In dimen- 
sioning a hexagon, the short diameter or distance across the flats (in this 
case, Ij in.) is always given rather than the distance across the corners, 
because it is by the short diameter that hexagon stock is designated. 

ASSIGNMENT 4 

14. Drawing from Objects. — Aside from the ability which he 
acquires to read drawings, the chief use that the shop mechanic 
has for a knowledge of drawing is in making occasional sketches 
for special tools or repair parts for machines. In the case of 
special tools, the drawing must often be made from a mental 
picture which the man has of what he wants, getting the prin- 
cipal dimensions from the machine to which it is to be adapted 
and from the w^ork to be done. 

Drawings may be made from actual objects in the case of 
broken machine parts, so that new parts can be made; or, in the 
case of pieces to be altered, so as to better adapt them to the 
work intended; or as a matter of making a shop record of a 
piece of work already done. For such work, one should have 
his calipers, both inside and outside, a scale or rule for taking 
measurements, and in some cases a protractor for measuring 
angles will also be needed. 

There are many points to consider in measuring an object and 
making a drawing of it, but a good mechanic is often better 
endowed with, common sense in this respect than is a regular 
draftsman, because he knows better the operations used in 
making a piece and can see what dimensions are most important. 
A few donHs by way of caution will point out some of the most 
common errors in this sort of work. These are taken from 
'^Don'ts for Draftsmen and Machinists," published by '' Machin- 
ery.'' 

Don't forget fillets. 

Don't repeat dimensions. 

Don't use fancy lettering. 

Don't put unnecessary finish on parts. 

Don't forget clearance for moving parts. 

Don't ever forget to put the scale on a drawing. 



PRINCIPLES OF MECHANICAL DRAWING 29 

Don't fail to sign all drawings which you make. 

Don't give dimensions in 32nds when 8ths are close enough. 

Don't put important dimensions where they ma}^ be overlooked. 

Don't omit minor details; it causes endless confusion and 
delay. 

Don't fail to use stock sizes of drills, reamers, etc., when pos- 
sible. 

Don't make three or four different views of a piece when one 
or two views \vill do as well. 

Don't forget center lines. A circle without its center lines 
looks like a bald-headed man. 

Don't put a lot of cored work on a '^ one-casting-only" job. 
A little extra metal is cheaper. 

Don't imagine rough castings come just like the drawing; 
they vary and you must allow for it. 

Don't give the same dimension twice, for it is liable to lead to 
errors when this dimension is changed. 

Don't leave some dimensions to be gotten by adding a lot of 
other dimensions together or by subtracting them. 

Don't forget that the molder despises sharp square corners; 
internal ones more than the external ones. 

Don't, when lines are close together, make arrows so that the 
workmen cannot tell which line they go to. 

Don't put all dimensions on, then all arrowheads; you are 
sure to miss some of the latter b}^ this method. 

PROBLEM 4A 

For this problem the student should make a mechanical drawing from 
some object as discussed in Art. 14. The following things are suggested as 
being suitable for this work: 

Bearing Cap (from lathe or steam engine) 

Stuffing Box Gland (from steam pump) 

Bracket (of any- kind) 

Plain Bearing Block 

Journal Brasses (from railroad car or engine connecting-rod) 

Valve Chest Cover (from steam engine or steam pump) 

Cylinder Head (from steam engine or pump or gas engine) 

Gear Box Cover (from automobile) 

Valve Rocker Arm (from gas engine) 
The piece selected should be made in one piece and should not have an}- 
threads or tapped holes, as the representation of screw threads has not been 
discussed as yet. 

If such objects, or models of them, are not available, problem 4B may be 
substituted. 



30 



SHOP SKETCHING 



PROBLEM 4B 

Fig. 36 shows a side and end view of a cast-iron bracket such as is used to 
support the cam shaft on a horizontal gas engine. It consists of a flat 
rectangular plate with foui- holes drilled through it, an arm strengthened by 
a deep rib, and a hub on the end drilled for the cam shaft. The bracket is 
fastened to a planed spot on the base of the engine by four f-in. cap screws 
through the holes in the base of the bracket. 




Bracket 
i- required cast irom 



Fig. 36. 




Fig. 37. 

The views shown here are not the best. The bracket would be shown to 
better advantage if the top view were drawn instead of the end view. The 
student is to make a drawing of this bracket using the side view and the top 
view. In Fig. 37 are shown roughly the views wanted. The student should 
select a scale that will make the drawing look well on the sheet. 






CHAPTER II 
ASSIGNMENT 5 

SCREWS AND SCREW FASTENINGS 

15. The Nominal or Outside Diameter. — The Nominal Diam- 
eter of any screw or bolt is the diameter at the top or outside 
of the threads. By nominal diameter we mean the diameter by 
which the bolt is known. This is the diameter given in the first 
column of the bolt table, page 34. Thus, a f-in. bolt measures 
f in. in diameter at the top or outside of the threads. 

16. The Root or Effective Diameter. — The Root Diameter of 
a screw is the diameter at the bottom or root of the threads. 
This is the dimension from which the strength of the screw is 

DEPTH OF THREAD 



/ — JpitchU — 




Fig. 38. 

calculated, because it is the smallest diameter and hence the 
weakest. The nominal and root diameters are shown in Fig. 38. 

17. Depth of Thread.— The Depth of the thread is the radial 
distance between the top and bottom of the threads; that is, 
measured in a direction straight outward from the center. 

18. Forms of Threads. — The most common thread forms are 
the V, U. S. standard. Square, Acme, Worm, and Whitworth. 
Other shapes may be designed to meet special conditions. Fig. 
39 shows the outlines of the above named threads. 

19. The V Thread.— The V thread has an angle of 60° between 
the sides and is pointed at the top and bottom. Its use is 
confined chiefly to small screws. 

3 .31 



32 



SHOP SKETCHING 



20. The U. S. Standard Thread.— The United States standard 
thread was designed by Mr. WiUiam Sellers of Philadelphia and 
recommended by the Franklin Institute of that city in 1864. 
It was later adopted in a modified form by the U. S. government 
and is now variously known as the Seller's, the Franklin Institute, 
and the U. S. standard thread. It is similar to the V thread 
with the exception that the top and bottom of the thread are 
flat, thus leaving a larger root diameter and therefore making a 






V Thread 



U.S. Standard 



Square Thread 




355 P 





Acme ThreAd 



WormThreadCB&S^td.) Whitworth Thread 
Fig. 39. 



stronger bolt than if the V thread were used. It is used generall}' 
for bolts, studs and cap screws. The width of the flat surface 
at the top and bottom of the threads is one-eighth of the pitch. 

21. The Square Thread. — The Square thread has not been 
standardized. It is used for heavy work to transmit motion or 
power, as in jack screws and screw presses, but each manufacturer 
has his own standards of pitch. It is quite common practice 
to use a pitch twice as great as on a U. S. standard bolt of the 
same diameter. The square thread is more difficult to cut than 
the other forms of threads. 

22. The Acme Thread. — The Acme thread is. a compromise 
between the square and U. S. standard threads. It is as deep as 
the square thread, but is stronger and easier to cut. It is used a 
great deal for feed screws, lead screws, etc., on lathes and other 
machine tools. 

23. The Worm Thread (Brown and Sharpe Standard).— This 
is used for the threads of worms in worm and worm-wheel combi- 
nations. It is really a form of gearing, but is cut in a lathe and 
is therefore given the name of thread. It is a much deeper 



SCREWS AND SCREW FASTENINGS 



33 



thread than the Acme, with the same angle (29°) between the 
sides of the threads. 

24. The Whitworth Thread.— The Whitworth thread is the 
standard used in England. It was designed by Sir Joseph Whit- 
worth in 1841, but has been slightly modified since that time. 
It is more difficult to form than either the V or the U. S. standard, 
as the thread tools must be ground so as to make the exact curves 
at the top and bottom. 

25. Pitch. — Usually the threading of a bolt or screw is described 
by telling the number of threads per one inch of length, thus — 
''8 threads per inch," or simply ''8 pitch." However, in giving 
the proportions of any given thread, we usually describe them in 
terms of the pitch. This is the distance from any point of a thread 
to the corresponding point on the next thread, as shown in Fig. 
38, and is designated by the letter P, as shown in Fig. 39. The 
pitch of a single-threaded screw is the distance the screw or nut 
will advance in one complete turn. Thus a screw having 8 
threads per inch has a pitch of J in. and would advance f in. in 
one complete turn. 

26. Bolts. — A bolt is a bar with a head on one end and a thread 
for a nut on the other. It is used to fasten two parts together 
by passing through them and clasping them together between 
the head and nut, as shown in the case of the two angles of Fig. 
40. Unless otherwise stated, it is understood that bolts have the 




Fig. 40. 



U. S. standard thread, as this thread is in common use by bolt 
manufacturers. Bolts are designated by the shape of the head. 
The kinds usually employed in machine work are the square head 
and the hexagon (or ''hex") head machine bolts (Figs. 41 and 43). 
The round or bar length of the bolt is called the stock, and 
carries on its end the thread for the nut. There are numerous 
special kinds of bolts used in special industries; for example, there 
are plow bolts, carriage bolts, stove bolts, etc. 



34 



SHOP SKETCHING 



DIMENSIONS OF U.S.5TANDARD B0LT5,HEAD5,g NUTS. 

ROU6H. 





SHORT DIA 
OF HEADS & 

NUTS 
MEX.& SQ 



DIST ACnOSS FLATS 



LONG d;ameter 

OF HEADS & NUTS 



THICKNESS 
HEXAGON &SQUARE 



HEXAGON SQUARE 




OiST ACROSS CORNEPS 
I 



HEADS NUTS 



fl 



CD: 




MEAREST 64"» 



ROOT 
OIAMETEPI 



5 

Q 

J7 

16 

J_ 

2. 

9. 
16 

5 
"S" 

3, 

4. 

7 

a 



1. 

6 

J. 

2 

3. 



2^ 



20 

18 

16 

14 

13 

12 

I I 

10 

9 

d 

7 

7 

6 

6 

5 

4i 

4- 
3i 



j_ 

z 
12. 

3Z 

11 
16 

25 
32 

21 
S 

31 
32 

JL 
16 

li. 
A- 

III 

>l 

16 



2^ 
4| 



37 

6^ 

11 
16 

5i 
64- 

29 
32 

I 64- 

li 

'64 

1^ 
' 64- 

m 
li 

23^Z 



^16 

oil 

"^16 

^64- 

^6^4 

332 



23 
32 

u 

32 

li 
32 

1^ 

li 
If 
li 

m 

23\ 

211 

^64. 

2^ 

-^16 

2^ 

^64. 

^32 

a23 

^64- 

3^ 

^64- 

4.2Z 

^64- 
^64- 
O32 



_!_ 

4- 

i9 
64. 

ii 
32 

2S 

64 

7. 
16 

31 
64- 

J7 
32 

5 
6 
23 
32 

12. 
16 

29 
32 



1-2- 

'32 

i| 
i| 
i| 

|3 
'A- 

lit 

2| 



4- 

16 

3 
8 

7 
16 

I 

2 

9 

16 

3. 

a 

I. 

4- 

j^ 

8 



6 

j_ 
4- 
3. 

8 
_L 

2 

3. 

A- 



2i: 
24 
2i 



13 
6^ 
j_ 
4- 

5. 

16 

23 

64 
27 
64 

15 
32 

IZ 
32 

41 
64 

3. 

4- 

55 
64 

II 
32 

32 

13. 
64 

11 
64 

rr 

32 

3, 

4 



2- 

-'^32 

2- 
^ 16 



.165 

,240 

.294 

.344 

AOO 

ABA 

.507 

.620 

73 1 

.837 

.940 

1.065 

1.160 

1.284 

1,491 

1.712 

1.962 

2.176 

2.426 

2.629 



SCREWS AND SCREW FASTENINGS 



35 



27. Bolt Heads and Nuts. — The heads and nuts of machine 
bolts may be either square or hexagonal, as desired. These 
have the same principal dimensions so that the same wrenches 
can be used on either. The table, page 34, shows the dimensions 
of the U. S. standard rough-forged nuts and heads. Finished 
heads and nuts are iV in. smaller in width than the dimensions 
given here. 

In representing a bolt head or nut on a drawing, we do not go 
to the trouble to lay it out precisely from the dimensions given 
in the table, unless the bolt itself is the main part of the drawing. 
If the bolt is only a detail of the drawing we generally use a simple 
system which represents very nearly the exact sizes and saves 
much time in drawing. In Figs. 41, 42, 43 and 44 are shown the 
different views of square and hexagon bolt heads as they are 



Square Head Bout 



Hexagonal Head Bolt. 





usually drawn. The views of Figs. 41 and 43 are usually pre- 
ferred because they indicate more clearly in the elevation that 
the heads are square or hexagonal. Figs. 42 and 44 both have 
two faces showing in the elevation and therefore might be 
confused. 

In drawing the square head of Fig. 41 the width of the square 
is made about If times the bolt diameter. The draftsman does 
this by eye. The height of the head in the front elevation is 
made half the width of the head or a little less than the bolt 
diameter. The height of a nut is made the same as the bolt 
diameter. The champfer (the bevelling of the corners on top) 
is shown by the full circle in the top view. In the front view we 



36 



SHOP SKETCHING 



represent this by an arc, with radius equal to the width of the 
head, drawn tangent to the top of the head. 

To represent the hexagonal head or nut (Fig. 43) the draftsman 
extends the lines representing the bolt stock. This gives one 
face of the head in the front elevation. One-half this width is 
set out on each side, for the other two visible faces. The top 
line is next drawn at a height a little less than the bolt diameter. 
The champfer is then shown. In the front face this is drawn 
Math a radius equal to the bolt diameter. On the side faces a 
radius about one-third as great is used. In drawing the top 
view of a hexagon head, we locate the center lines and draw a 
broken circle to represent the stock of the bolt. With the 
diameter of the bolt as a radius we then draw a light construc- 
tion circle, and in this we draw a hexagon as shown in Fig. 
35. We then erase the construction circle. Within the hexa- 
gon and just touching each side of it, we draw a circle to repre- 
sent the champfering or bevel on the top corners. 

28. Thread Conventions. — Draftsmen usually show threads 
in side view by the conventional straight-line method shown in 
Figs. 45 and 46. The long light lines represent the tops or 




•^ 


p>v 






If 


■A 


\\ 


/I 


\\^ 


/J 


^ 


'jy 




R.H. THREAD, 

Fig. 45. 



l.h.threXd. 
Fig. 46. 



''lands" of the thread while the short heavy lines represent the 
bottoms or "roots" of the thread. These lines should be evenly 
spaced and should be given a slight slant. On a single-threaded 
screw, one end of a light line should lie approximately opposite 
the other end of its adjacent heavy line. Ordinarily no attempt 
is made to make the spacing of these lines comply exactly with 
the pitch of the screw. 

The method of representing the end view of a screw is also 
shown in Figs. 45 and 46. The circle representing the ''lands" 
of the threads is drawn solid, while the root circle is broken 
because it represents a hidden surface, namely, the bottom of 
the thread. 

29. Right-hand and Left-hand Threads. — The thread shown 
in Fig. 45 is a right-hand thread; that is, to screw a nut on to 



SCREWS AND SCREW FASTENINGS 



37 



such a thread it would be necessary to turn it in a right-hand or 
clockwise direction. Compare this with Fig. 46, which shows a 
left-hand thread. Note that the thread lines in this figure are 
given a slant opposite to those shown in Fig. 45. Where the 
stock of the bolt ends, a heavy object line should always be 
shown as in these figures. At the place where the thread termi- 
nates a light line should be drawn straight across the bolt. The 
end of the stock should always be rounded, but its length should 
only be dimensioned to the corner where the rounded end begins 
and not to the extreme tip of the bolt. 

Left-hand threads are not nearly so common as right-hand 
threads; hence, when a left-hand thread is desired it should be 
marked, L. H. Thread. It is not generally customary to mark 
right-hand threads as such; if marked, we would use the note 
R. H. Thread. 

30. Tapped Holes. — The thread which is cut in any piece of 
metal to receive a screw is said to be 'Happed." Ordinarily a 
hole is drilled in the piece to the same diameter as the inner 
diameter of the thread. A 'Hap" (which is somewhat like a 



e>-^3 



I ■! 



----I 









Fig. 47. 

hardened bolt, having grooves for the cut metal to escape and 
sharp cutting edges on its threads) is then screwed into this 
hole, cutting a thread as it advances. 

In representing a tapped hole in a drawing, the plan view of 
the hole is very simple. As shown in Fig. 47, the plan view 
shows a sohd inner circle representing the hole drilled for the tap ; 
a broken outer circle surrounds it to represent the hidden threads 
cut by the tap. This outer circle is drawn to the nominal diam- 
eter of the screw. 



38 



SHOP SKETCHING 




Hex Head Bolt 
i-required machine steel 

SCALE. S"=r 



Fig. 48. 




|:gTMREAD, & PER INCH 



Fa.ce Plate 
i-required cast iron 

SCALE 3"= l' 






Fig. 49. 



SCREWS AND SCREW FASTENINGS 



39 



The representation of a tapped hole in elevation must natu- 
rally be all in broken lines, since the hole is hidden from sight in 
this view. Fig, 47 shows the most common method of showing 
this. The threads are represented just as in Fig. 45, but with 
all broken lines. The hole at the left is drilled and tapped clear 
through the piece; that at the right, only part way through. 

Fig. 48 shows a drawing of a li in. X3f in. hex head machine 
bolt with nut using the conventional methods of showing the 
threads and the head and nut. The actual heights of head and 
nut and the true width (from the table, page 34) are given for 
the guidance of the blacksmith and machinist in making the 
bolt. 

Fig. 49 shows a drawing involving several tapped holes. This 
is a special face plate for a lathe. It is to be tapped with a ^-in. 
standard bolt tap at three points equally spaced on a circle of 
4f-in. diameter. These holes are for studs for attaching a special 
fixture to the face plate. In the center of the plate is an in- 
ternal thread for screwing the face plate onto the spindle. The 
note referring to this hole is marked THREAD instead of TAP. 
because this is to be cut with a thread tool in a lathe in order to 
make it absolutely true. 

31. Other Thread Conventions. — In Figs. 50 and 51 are shown 





Fig. 51. 



other conventions that are occasionally seen. The convention 
at B in these figures is especially simple and convenient for 
sketching purposes but has the great disadvantage that it 
bears no resemblance to screw threads and hence is not 
recommended. 

32. Method of Drawing Square Threads.— In looking at any 
bolt, the threads present a slightly curved appearance as shown 

4 



40 



.SHOP SKETCHING 



by the square threads in Fig. 52. In representing the threads on 
drawings of bolts, we use straight Hues running across the bolt 
as in Fig. 48. The same principle is applied to showing square 
threads, as illustrated in Fig. 53. Whenever a square thread, or 
any thread other than the U. S. standard, is shown on a sketch, 
it is well to add a note calling attention to the fact and stating 
the number of threads per inch; thus: 3 SQ. THDS. PER INCH. 
It is generally simpler to show a square thread or other special 





Fig. 52. 

thread on a small piece by the '' thread line" method of Fig. 45, 
being careful however to note that it is a square thread, 

33. Cap Screws. — A cap screw is similar to a bolt, but is used 
without a nut. The head may be either square or hexagonal. 
A cap screw is used by passing it through one of the pieces to be 
fastened together and screwing the threaded part into the other 
piece. Fig. 54 shows the method of using cap screws in fastening 
a bracket to a machine. In this figure, the metal around the 
cap screw is broken away to show the cap screw clearly. 




Fig. 53. 



The heads of cap screws are smaller than those of bolts. The 
widths (or the short diameters) of hexagon heads for cap screws 
are standardized as follows: 

For screws up to and including i\ in., the heads are made 
-r^ in. wider than the screw stock. 

For sizes i in. and larger, the heads are made J in. wider than 
the screw stock. 

For square heads, the width is J in. greater than the stock for 



SCREWS AND SCREW FASTENINGS 



41 



sizes up to and including f in. Above f in. the heads are J in. 
wider than the stock diameter. The height of the head is equal 
to the diameter of the screw. The top of the head is not flat like 
a bolt head, but is rounded with a radius equal to the long 
diameter of the head. Cap screws can also be obtained with smy 
of the other heads shown in Fig. 55. 




Fig. 5-i. 

34. Machine Screws. — Machine screws are used fcr the same 
purpose as cap screws, but for small work only. Machine 
screws are generally used for sizes below i in. They are made in 
screw gauge sizes and sold by the gauge numbers instead of the 
fractional inch sizes. 

Fig. 55 shows some of the different kinds of heads for machine 
screws. The square and hexagonal heads are the only ones on 



dp oh CO W ^ 



SQUARE HEXAGON 



FLAT FRENCH OR 

OVAL- 
COUNTERSUNK 



OVAL FLAT BUTTON 

riLLISTER FILLISTER 

MACHirsE Screw Heads 
Fig. 55. 

which a wTench can be used. These heads are usually thicker 
and of smaller diameter than the U. S. standard bolt heads. 
All of the other heads are provided with slots for a screw driver. 
35. Set Screws. — A set screw is used to fasten two machine 
parts together by screwing through one part and pressing against 
the other. For example, in fastening a wheel to a shaft, the set 
screw passes through the hub of the wheel and presses against 



42 



SHOP SKETCHING 



the shaft. It is a poor fastening for transmitting power, and 
should not be used if a key or square shaft can be used. 

Fig. 56 shows some of the common forms of heads for set screws. 
The thickness of the head and the wadth across the flats are 
ordinarily made equal to the diameter of the screw. The 
headless set screw, in which a screw driver is used to turn it into 
place has the advantage that it can be screwed in so that there 




NECK 






square head low mead headless 

5e.t Screw Heads. 
Fig. 56. 



HOLLOW HEAD 



are no projecting parts to catch the clothing. It has the objec- 
tion, however, that one side is apt to break off. To remedy this 
defect, a hollow head set screw has been designed. This requires 
a special wrench bent from a hexagon steel bar. 

Set screws are sometimes '^ necked" under the head. This is 
done by cutting them down so that the diameter is a little less 







ROUND 



CONE 



CUP 




i;j 



ROUND 
PIVOT 



3et 5crew Points. 
Fig. 57. 

than that of the root of the thread. This makes the ''neck" the 
weakest part of the screw so that, if the screw should break when 
being tightened, it Avill break at the neck instead of in the hole. 
The most common forms of set screw points are shown in Fig. 
57. Any of the heads of Fig. 56 can be used with any of these 
points. In using a set screw on finished work, where the point 



SCREWS AND SCREW FASTENINGS 



43 



of the screw is liable to burr or roughen the part against which 
it presses, a round brass piece called a ''gib" is often dropped into 
the tapped hole so that the screw point presses against the gib 
and the gib against the part to be fastened. Set screws are made 
of steel and are usually case hardened. 

36. Multiple Threads. — In all of the threads that we have 
considered so far, there has been but a single thread on the 
screw. It is sometimes desirable, however, to have more than 
one. If there are two separate threads on the screw, it is called 
a double thread, if three threads, a triple thread; and if there are 
four threads, it is a quadruple thread. 

In Fig. 58 is shown a double-thread screw. Copipare it with 
Fig. 38. The outside diameter of the screw, the root diameter, 




Fig. 58. 

the depth of the threads, and the pitch are the same in both 
cases, but the amount that the thread advances in one turn or 
revolution of the screw is twice as great in the double thread as 
in the single thread, and the lines of the threads in the sketches 
must be given a correspondingly greater slant than in the case of 
single threads. 

37. Lead. — The distance that the thread advances along the 
screw per revolution is called the lead (pronounced as if spelled 
"leed"). For a triple thread, the lead would be three times the 
pitch. Multiple threads are used when it is desired to secure a 
greater advance per revolution, without reducing the root 
diameter of the screw. Any of the threads of Fig. 39 may be 
made multiple. Wherever a multiple thread appears on a 
sketch, a note should state the fact, giving complete information. 

PROBLEM 5A 

Fig. 59 shows a sketch of a valve stem for a 3-in, globe valve. This 
sketch only shows one view of the stem, but it will be understood that it is 
5 



44 



SHOP SKETCHING 



round at all points along its length except where the note indicates that 
it is to be made square. The hand wheel for operating the valve has a 
square hole which fits the square on the stem. A f-in. standard hexagon 
nut is then screwed on the small threaded end of the stem to hold the hand 
wheel. The valve disk has a grooved pocket on it which fits around the 
head shown at the right7hand end of the stem. There are two special 
features of the sketch that should be noted. The diagonal lines running 



SQUARE 



U.S. 5TD. 
THD. R. M. 




R. M. SQ. THREAD 



6 PER I IN. 



=l«0- 



lO 



--JM 
'A- 



Stem for 3" Globe V^^lve. 

1-REQUlRE.D MACH. STEEL 
SCALE 3"= l'. 



Fig. 59.. 

across the squared part indicate the extent of the part that is squared. 
This is a common convention for indicating, on a rough sketch, the side view 
of a squared part. The threaded parts are indicated only by notes. This 
is permissible for a preliminary sketch. 

Make a drawing of this stem showing the square threading by the method 
of Fig. 53 and the U, S. S. thread on the end by the convention of Fig. 45. 
Also show the end view of the stem from the smaller (left) end. 

PROBLEM 5B 

For sketching from objects or models, the following lists are suggested, 
at least one drawing to be made from each Kst. 



hist A 
Square head machine bolt and nut 
Hexagon head machine bolt and nut 
Eyebolt 

Turnbuckle and rod ends 
Tool post and sot screw 



Lint B 
Lathe dog and screw 
Lathe cross feed screw 
Screw for jack screw 
Vise screw 
Bench screw 



CHAPTER III 

SECTIONS 

ASSIGNMENT 6 

38. The Use of Sections. — The uses of broken lines to show 
hidden parts were explained in Chapter I, Art. 6. Broken lines 
are not always satisfactory and are often confusing,- especiall}' if 
very numerous. For these reasons, the method of showing 
objects in section is frequently used to show interior construc- 
tions. This method consists in cutting away the parts which 
hide those we want to show, thus allowing the hidden parts to 
stand out in full view. This is called cross-sectioning, or section- 
ing. Such a view is called a cross-section, or more simply, a 
section. As a simple illustration, we have in Fig. 60 two ordinary 
views of a plain cast-iron collar, the hole being indicated in the 



<i) 



Fig. 60. 



A 




SECTION ON UNE A-B. 



SECTION ON LINE A-B. 



Fig. 61. 



Fig. 62. 



right view by the broken lines. Fig. 61 shows the same collar 
but with the hole shown by a section view. The end view is 
still shown in the usual manner, but, instead of the side view 
being shown by a front elevation, we imagine that the front half 
of the collar in this position has been cut away to show the 
inside. The light diagonal lines across the places where the 
metal would be cut form what is called the cross-hatching. 
These lines are drawn lightly about yV in. apart, and usually 
at an inclination of about 45 degrees. If we imagine that the 
cross-hatching lines represent the saw marks, then we can al- 
ways tell what part is to be cross-hatched. When there is a hole 
or opening in the object there will, of course, be no saw marks and, 
6 45 



46 



SHOP SKETCHING 



hence, there is no cross-hatching in the area representing such 
hole or opening, as is clearly shown in Fig. 61. 

Let us suppose that this collar is fastened to a shaft by a set 
screw. In order to show the arrangement of the shaft and 
screw inside of the collar, we can cut the collar in the same way, 
as shown in Fig. 62. To actually cut the collar we would also 
have to saw into the shaft and screw, but it is customary to con- 
sider them as not being cut, as it would only increase the work of 
making the drawing and would not make the construction of the 
collar any clearer. 

As a general rule it may be stated that: Bolts, screws, shafts, 
keys, arms of pulleys, etc., are not shown in section when cut along 
the line of their greatest dimension, that is, lengthwise. If the sec- 




FiG. 63. 



tion cuts across a shaft, screw, or similar object it might, in such 
a case, be cross-hatched. 

Fig. 63 shows a section of a gland for a stuffing box. The 
flange around the top projects all the way around. Conse- 
quently, in the section elevation, the lower edge of the flange 
might be shown by a broken line crossing the body from a to h. 
It is much better, however, to keep the section free from such 
complications and only depend on it to show the interior of the 
object. If it is necessary to show both inside and outside of the 
same view of an object it is better to use the principle of half 
sections. 

39. Half-sections. — When a figure is symmetrical about an 
axis (that is, alike on both sides of its center-line), it is a good 



SECTIONS 47 

plan to show only one half in section. Such a drawing is known 
as a " half-section'^ because we have only sawed half way through. 
Fig. 64 shows a half-section of the same collar as in Fig. 62. In 
Fig. 64 we really consider that the upper front quarter of the 
collar is removed. The horizontal cut thus produces a surface 
along the horizontal center-line, which is indicated by a heavy 
object line on the center-line of Fig. 64. Any peculiarities of 
the outside of the object would be shown by one half of the 
view, while the inside would be shown by the sectioned half of 
the view. 

If a section passes through the center of a hole that is tapped 
with a right-handed thread, the thread is shown in the conven- 
tional straight line method, but the thread lines slant in a direc- 
tion reverse to those of a right-handed outside thread. The 
threads which appear in the section are those on the far or rear 
side of the tapped hole; see Fig. 65. Fig. 64 shows the collar 

5jn 



i 



half section on une. a-b . half section on une a-b. 

Fig. 64. Fig. 65. 

with the set screw in place. Fig. 65 shows the same collar with 
the set screw removed, and the tapped hole which receives it 
exposed to view. 

Half-sections often show the interior construction of an object 
so well that many broken lines may be conveniently omitted 
from the other half of the view. In the view that is half-sec- 
tioned, avoid running dimensions from the sectional part to the 
full part; rather show them in the other view of the object, 
unless the part dimensioned is shown by a full line in both parts 
of the view. Also avoid placing dimensions, or running exten- 
sion or dimension lines across the cross-hatched portion of the 
view, although this is sometimes necessary. 

Always put the cross-hatching on after putting on the dimen- 
sions, so that in case it is necessary to put a dimension in the 
cross-hatched area, a break may be made in the cross-hatching. 

It does not make any difference in which direction the cross- 
hatching lines slant, so long as they make an angle of 45° with 



48 



SHOP SKETCHING 



the horizontal, except that on the same piece they should all 
slant in the same direction. You will find it most natural, 
however, to begin in the upper left-hand corner of the view to be 
cross-hatched. The spacing can be judged by the eye, the lines 
being about iV in. apart. 

40. Broken Sections. — Cutting planes need not always be 
continuous; they are very often broken or '^ zigzagged" so as to 
show the construction of the object in different planes. Fig. 66 
shows a drawing of a bearing block. The cutting plane is passed 




HALF SECTION ON LINE A-B-C-D-E, 

Fig. 66. 



along the lines ABODE in the upper plan so as to show the in- 
terior construction at the oil hole and also at a bolt hole. 

Note that the surface OD where the cut is set over is not 
indicated in the section view. Since the bearing block is sym- 
metrical about its axis, the other half may be shown conveniently 
as a full elevation view. When a section plane follows a devious 
outline as in this case, it is shown in the plan by the usual center- 
line convention. Appropriate letters and notes should show 
where the cutting plane is passed, and the section view should 
be labelled accordingly. It is general practice to omit such 
notes where the cutting plane is passed along the main center- 
line, as in Figs. 61, 62, 63, 64, and 65. Notes were used on these 
drawings merely for the information and direction of the student. 



SECTIONS 



49 



PROBLEM 6A 

Fig. 67 shows a push-rod bushing or guide, used on a gasoline engine to 
guide the push-rod to the valve. This bushing is used with the hole ver- 
tical, being screwed into a hole tapped in the crank case. The upper part 



4' DRILL. 



'16 




(4- R.H.TMDS. PER l" 



^ 



mioo 



^ 



2 niA 




Push Rod Bushing 
l-reouired cast iron- 
sc/^l-e: 6"= i' 



Fig. 67. 

is bored to guide the ^-in. push-rod, while the lower part is enlarged to jf in, 
to receive a helical spring used to retiu"n the push-rod and roller to place. 
The natural position of the bushing is shown in Fig. 68. 




Fig. 68. 



Make a full-size drawing of the bushing, giving the views shown in Fig. 68 
and making the side elevation a full-section view. Remember that this 
will expose the broken lines of the bored holes as full lines. In making a. 



50 



SHOP SKETCHING 



section of an object that is threaded on the outside like this, it is necessary 
to show the threads as actual V-shaped notches on the sides of the object as 
in the drawing of the V thread, Fig. 39. As this bushing is made from a 
solid piece, the cross-hatching should all slant the same way. 

PROBLEM 6B 

The following objects are suggested, from which at least one should be 
sketched : 

Shaft collar 

Pipe tee or elbow 

Pipe flange 

Stuffing box gland 

Any small solid pulley or gear blank. 

ASSIGNMENT 7 

41. Partial Sections. — When a section is needed to show the 
interior construction of a machine part in only one particular 
place, we can imagine the metal in front of that place broken 
away so as to leave the hidden parts exposed. This is the 
method that was used to show the cap screws in Fig. 54. To do 
this, a wavy line is drawn free-hand around the part, and the 
proper cross-hatching is placed inside the broken space. This 
makes it appear as if the metal had been broken away roughly. 

42. Revolved Sections. — The necessity of drawing an extra 
view of an object may frequently be avoided by the use of a 




Fig. 69. 



revolved section. For an example of the revolved section see 
Fig. 69. Notice that it consists in drawing a cross section of the 
handle on the plan view, thus doing away with the necessity of 
making a separate end view in order to show the shape of the 
section of the handle. 

Fig. 70 shows how a piece of an object may be broken out to 
leave room for the revolved section. This is especially desirable 



SECTIONS 



51 



in this case because the arm tapers, and consequently the lines of 
the lower flange would cross the section if it were drawn on the 
object, as in Fig. 69, without breaking away the arm. 

Fig. 71 shows a common method of showing sections where the 
sections are different at different points along a piece. The 
sections are drawn off the view but the lines at which they 
are taken are located on the drawing of the object. This method 
















r-^. .. -r~ 


_. 




rrJc 




' 


PC 













Fig. 70. 



is frequently used in showing the shape of long parts such as 
lathe legs, connecting rods, etc. 

Pulleys, hand wheels, gears, and other such circular objects 
are usually shown by two views, one of which is a section. 

Fig. 72 shows a complete conventional drawing of a six-arm 
pulley. It will be noticed that the section plane is passed along 
the vertical center-line, but that the arms which would really be 
cut in making the section are not cross-hatched and, instead, the 




SECTION ON A-B 



section on c-d 
Fig. 71. 



section is shown as if it passed just to one side of the arms. As 
stated in Article 38, it is the general practice not to cross-hatch 
the arms of pulleys, hand wheels, etc., when cut lengthwise. 
Only the hub and rim should be cross-hatched. It should be 
noted that the inside surfaces of the rim should be shown by full 
object lines all the way across, as if the section plane had been 
passed just in front of the arms, thus showing only the rim and 
hub in section. 



52 



SHOP SKETCHING 



tra 



=5 



4. ► 



'■'■'■>^'->- 



^^ 



16 



^ 



fel 



^^ 



lllLUsk 



=t 






"T 2 




Fig. 72. 



foN--j>*- 




FiG. 73. 



SECTIONS 53 

For greatest strength, the keyway should always be shown on 
the center-line of one of the arms, and not midway between two 
arms. The face of this pulley is 4 in. Instead of being flat or 
straight, it is crowned. Different authorities recommend that pul- 
leys should be crowned (or have a rise of ) from iV in. to | in. per 
foot of width, but | in. per foot of width is a good average. The 
crown is for the purpose of keeping the belt on the pulley. Pulleys 
for use with shifting belts should be straight or flat, that is, with- 
out crowning. 

Note that the diameter of the pulley is marked TURN. This 
means that enough stock must be left on the pattern so that the 
pulley can be turned down to the required diameter. 

A revolved section on one of the arms is used to give a clear 
idea of its cross section. 

Quite often we encounter wheels of various kinds which have 
an uneven number of arms or spokes, so that no two arms have a 
common center-line. Fig. 73 shows a drawing of a hand wheel 
with three arms. Notice particularly how the arms are shown. 
In the section view only two arms are shown and they are shown 
full length as if they were directly opposite each other on the main 
vertical center-line of the hand wheel. The right-hand view is 
depended upon to show the number and arrangement of the 
arms, and also to show a revolved section of one of them. If we 
attempted to show them in the section view as they really 
appear when the hand wheel is in this position, the lower arm 
should appear shortened. It would be more difficult to show 
such inclined arms as they really are and would make the drawing 
less easy to read. 

43. Shortened Views. — Fig. 70 illustrates a common practice 
in showing long slender objects, of breaking and leaving out 
part of the length in order that the piece may be shown on the 
paper without using too small a scale. The long arm in Fig. 70 
is broken and the two end pieces placed closer together than they 
would actually be if the full arm had been drawn. This permits 
the use of a larger scale on the parts shown. The full length of 
the arm should, of course, be given in dimensioning. 

PROBLEM 7A 

Fig. 74 shows two views of a gate valve hand wheel. Draw the views 
shown in Fig. 75, making one view a half-section, sectioning the upper half 
and drawing an outside view of the lower half. 



54 



SHOP SKETCHING 



I 




32 

Hand Wheel 

FOR 

©"Gate Valve, 
i-required cast iron 

SCALE 3"=l'. 



Fig. 74. 



SECTIONS 



oo 



Note that the square hole for the valve stem is tapered from 1 in. to | in. 
Remember that the spoke is not to be cross-hatched. 

In the majority of pulleys and wheels of various sorts, as in this case, the 
section of the spokes is an ellipse. An approximate ellipse can be drawn 
very readily by the method shown in Fig. 76. To start with, we usually 
have the long and short diameters of the ellipse. Lay these out and call 




Fig. 75. 

their half lengths a and b. Lay the length of b in from m, thus locating the 
point d. With the eye, divide the remaining distance from d to o into 
three equal parts. With the compass, swing one of these parts back to 
the other side of d, thus locating point c. This point c is the center of an 
arc forming the ends of the ellipse and the radius Ro is the distance mc. 

The distance en, the remainder of the long diameter, is the radius Ri for 
the flatter sides of the elHpse. 




Fig. 76. 

PROBLEM 7B 

Make a drawing from some object or model involving sections, such as 



Hand wheel 
Flywheel 
Pulley 
Trolley whee] 



Lathe leg 

Scythe or sickle blade 

Solid WTench 

Drill press table bracket 



56 



SHOP SKETCHING 



ASSIGNMENT 8 

44. Assembly Drawings in Section. — So far, the drawings have 
all been of single parts. Such drawings would be used in the 
shops to guide the men in the manufacture of the various pieces. 
In the case of a machine made up of several parts, we would have 
such detail drawings from which to make the several parts. 
It would also be necessary to have a drawing to show how these 
parts were to be put together. This drawing, showing the assem- 
bled machine, is called the Assembly Drawing or the Assembly. 

Section views as applied to assembly drawings are highly im- 




y-\ 2-^eOLTS 



2.4" Step Bearing. 



Fig. 77. 



portant because of the simple and graphic manner in which they 
show the relation of the parts to each other. Assemblies in 
section are also freely used as illustrations in trade journals, in 
United States Patent Office drawings, in catalogues, and else- 
where, where line mechanical drawings might not be understood 
by people who had occasion to refer to them. 

Assemblies may be drawn either wholly or partly in section, 
just as in the case of the sectioning of detail parts. 

Fig. 62 shows a full section of an assembly — a collar secured 



SECTIONS 



57 



to a shaft by means of a set screw. Fig. 64 shows the same 
assembly in half section. Half sections are sometimes preferable 
because they show the exterior as well as the interior construc- 
tion. As in detail drawings, so in assemblies, it may be stated 
as a general rule that: Bolts, screws, shafts, arms of pulleys, 
keys, etc., are not shown in section when cut along the line of their 
greatest dimension. 

Fig. 77 shows a half -section drawing of a step bearing. Such a 
bearing is used to support a vertical shaft at its base. It consists 
of a cast-iron housing enclosing a bronze footing. Cast iron 
is a poor bearing metal; hence, the use of the bronze footing. The 
footing is cupped on one side to a radius of 2h in. The end of 
the shaft is rounded to the same radius. Thus the shaft end and 
bearing are segments of a ball and socket. This keeps the 





Fig. 78. 



Fig. 79. 



shaft centered in the step and yet allows for some flexibility of 
direction. 

Fig. 78 shows a full section view of a simple globe valve. 
This section' shows clearly the relations of the various parts. 
The valve stem D has a hand-wheel C at the top and a disk / at 
the bottom. The hand-wheel is secured to the stem by means of 
the set screw A which seats itself against the washer B and is 
tapped into the stem. The stem, in conformance with the 
general rule, is not sectioned, but the upper part of it is broken 
away to show more clearly the method of attaching the hand- 
wheel. The stem has a square thread which engages the thread 
in the hub H. The packing G is retained in place by the gland F, 
which in turn is caused to compress the packing by screwing 



58 SHOP SKETCHING 

down the cap E. The hub H is tapped into the body of the 
globe valve. It will be seen that the lower end of the stem forms a 
thin round head. The lock nut M above this ring is tapped into 
the valve disk J below it. The valve disk is thus responsive to 
any movement of the valve stem and its hand-wheel. The valve 
disk J is subjected to severe usage in service and it is, therefore, 
necessary to regrind or renew it from time to time. The arrange- 
ment shown in this view permits of such renewals quite readily. 

As in detail drawings, so in assemblies, a section does not 
always follow a single straight line through the object. Fig. 66 
showed such a case, where the section plane was shifted to show 
the details at different points. If bolts were shown in the bolt 
holes of this figure it would become an assembly and thus serve 
as a good example of an assembly section with a somewhat 
complicated section plane. 

Fig. 79 shows a drawing of a globe valve in which only part of 
the body has been broken away. Only enough has been broken 
out to show the construction and relation of the important parts 
which are shown in section. The rest of the drawing is an exte- 
rior view and serves to show the external appearance of the valve. 
In this way, one drawing serves to show practically the entire 
form and construction, both inside and outside. 

45. Conventions for Cross-hatching. — In showing a single 
object in a section drawing, it is generally considered best 
practice to do the cross-hatching with lines of uniform weight, 
spaced about yV in. apart. In section assembly drawings it is 
necessary to make some distinction between the different pieces. 
This is done by using different kinds of cross-hatching lines for 
different materials and by inclining the lines of adjacent parts in 
different directions." An examination of Figs. 77, 78, and 79 
shows how the lines are given opposite slopes on pieces that touch 
each other, so that it will be more evident that they are different 
pieces. It should be noted well that the slant of the cross-hatch- 
ing of each part is the same for that part wherever it is shown. 
For instance, in Fig. 78, the sectioning for the cap E is alike in 
both halves, while the same rule applies to the hub H and the 
various other parts. It may be stated as a fixed rule without 
exception that: In an assembly section, each piece must have the 
same cross-hatching throughout. Note also how the section lines 
of the various parts in contact are, as far as possible, at right angles 
to each other. 



SECTIONS 



59 



Fig. 80 shows a quite common system of cross-hatching for 
different materials. Fig. 81 shows a much simpler system, 
that is quite often used but that does not cover as wide a range of 




CAST IRON 




CAST STEEL 




LEATHER 




MACHINE STEEL 




LEAD o» BABBITT 





MALLEABLE IRON 




NICKEL STEEL 




ALUMINUM 





BRASS OR BRONZE 




COPPER 




GLASS 




concrete rubber o« vulcanite 
Fig. 80. 



WOOD 




CAST IRON. 



WROUGHT 
IRON. 





BRASS, 

BRONZE,©'' 

COPPER. 




BABB\TT, 

LEAD, OR 

XIN. 



metals. There are no fixed rules governing these, as different 
drawing rooms have different standards. Each man should learn 
and use the standards of his own shop. It is becoming quite 



60 



t^HOP SKETCHING 



general to use the plain cross-hatching (cast-iron in Figs. 80 and 
81) for all drawings of single parts, stating the material in the 




title. Then, a system sufficiently elaborate to cover all the work 
of a shop is used on assembly drawings. 

Fig. 82 shows a broken section assembly of one end of a 



SECTIONS 



61 



connecting rod using the conventions of Fig. 80. Instead of 
running the whole length of the drawing, the section is discon- 




BoDY - Cast 5teq. 



Screw- Mach. Steel 



DETAILS 

FOR 

12" TON J/^CK SCREW 



Fig. 83. 



tinned by a wavy line, which makes it look as if we had sawed 
into the rod endwise and then broken the piece out. The section 
is thus broken to avoid the useless sectioning of the body of the 



62 SHOP SKETCHING 

rod. The revolved section gives an idea of the shape of the body 
of the rod. The cross-hatchings tell the materials of the different 
parts and, by being inclined at different angles, enable the 
student to pick out the different pieces. The body of the rod is 
machine steel, as is also the strap around the end. The boxes 
are made of cast-iron lined with babbitt. They are adjusted 
and secured in position by a steel wedge which is raised and 
lowered by means of two cap screws, tapped into the wedge. 
Notice that the bolts are not sectioned and that their dimensions 
are given by notes rather than by actual dimensions on the bolts. 

General assembly drawings should not show dimensions of 
minor details. Assembly drawings should show only those di- 
mensions which are necessary to show how the parts are to he put 
together and those which show the working capacity or strength of 
the mechanism. 

46. Conventions for Pencil Work. — For single parts, use the 
cast-iron convention for all materials and indicate the material 
in the title. 

For assemblies drawn with instruments, use the conventions 
of Fig. 81 because, wdth the single exception of wrought iron, 
these require only one weight of line. For any material not 
shown in Fig. 81, use the convention for the nearest similar 
material, or the cast-iron convention, and then label the part 
with a note telling the material. 

For freehand assembly sketches, always use the cast-iron con- 
vention and label all parts with notes. 

PROBLEM 8A 

Fig, 83 shows the details of a jackscrew. Make a complete assembly 
drawing of this jack in section, showing all parts put together in their proper 
positions. Do not section the screw. The upper end of the screw should 
be shown riveted over slightly, to hold the cap in place. 

PROBLEM SB 

Make a section assembly drawing of one of the following, or similar 
objects, from the actual objects: 
Flanged shaft coupling 
Oldham shaft coupling 
Universal joint 
Grease cup 
Flanged pipe coupling 



CHAPTER ly 

ASSEMBLY AND DETAIL DRAWINGS 

ASSIGNMENT 9 

47. Assembly and Detail Sheets. — Every machine or mechan- 
ism containing several parts should be represented by both as- 
sembly and detail drawings. The assembly shows how the 
various parts are related to each other and how they are put 
together; the detail dra^\dngs are used by the mechanic in making 
the separate parts. 

If the mechanism involves a large number of parts, there will 
be a single assembly drawing and one or more sheets of details. 
There may be a separate detail drawing of each part, or several 
details may be shown on one sheet. If a mechanism contains 
only a few parts, the assembly and the details ma}^ be shown on 
a single sheet. In this case, the usual practice is to place the 
assembly drawing on the upper left-hand corner of the plate, 
the rest of the plate being given over to the dra^vings of the 
details, as in Figs. 84 and 85. 

In making detail sheets, the details are sometimes drawn on 
the plates in the logical order in which they occur in the machine; 
that is, adjacent parts in the machine are drawn adjacent to 
each other on the detail sheets. Sometimes the details of units 
of the machine which are to be made, and perhaps assembled, 
in one part of the shop, are grouped together on the detail sheets. 
In other cases, it maj^ be convenient to group together the 
details of sifnilar parts which are to be made by the same me- 
chanic or department. For instance, we may place together in 
one group the details of all shafts required; in another group we 
may have all the gears; in another group all the bolts, screws, 
and other parts to be made on screw machines. The choice of 
any such methods as above noted will be determined largely 
by the local conditions governing the manufacture of the ma- 
chine and by the number of parts to be shown. 

It is generally necessary to make mechanical drawings to 
some convenient scale. The space allotted to each detail should 
8 63 






64 



SHOP SKETCHING 



bear some reasonable proportion to the space allotted to other 
details. In other words, a comparatively small and insignificant 






< L ui i vO 
L < 

0,?Z N 




00 

6 



part should not be drawn to a large scale while a larger and 
much more important part is drawn to a much reduced scale. 
If, however, a certain small part is highly important and compli- 



I 



ASSEMBLY AND DETAIL DRAWINGS 65 

cated in design, it may be advisable to draw it to a large scale in 
order to show it clearly and to emphasize the fact that it should 
be accurately made. Always strive at balance, so that the space 
given to each detail will be proportional to its importance and size. 

The detail drawing of each part should be complete and give 
all necessary information. Beneath each detail there should 
appear a title or ''legend" giving the name of the part, the 
number required for one machine, the material of which it is to 
be made, whatever finish, if any, is required, and the scale, if 
different scales are used for the details. As a general rule the 
same scale should be used throughout. No title or legend is nec- 
essary beneath the assembly drawing, except possibly the word 
Assembly. 

The title for the whole plate is usually placed in the lower 
right-hand corner. If the plate contains both assembly and 
details, the title for the plate may appear somewhat as follows: 

FOLLOW REST 

FOR 

12'' ENGINE LATHE 

If the plate contains the assembly drawing only, the title of the 
plate mil appear thus : 

FOLLOW REST 

FOR 

12" ENGINE LATHE 

ASSEMBLY DRAWING 

If the plate contains onl}^ the dra^vings of details, the title of the 
plate will appear thus: 

DETAILS OF FOLLOW REST 

FOR 

12'' ENGINE LATHE 

There should also appear the scale, the date, the filing number 
and the names of the various draftsmen involved in making the 
drawing. 

Fig. 84 shows a complete mechanical drawing (assembly and 
details) of a follow rest for a 12" engine lathe. Note carefully 
the general dimensions given in the assembly drawing. Note 
also the proper manner of showing sizes of bolts, set screws, etc., 
on an assembly drawing. The detail of each part gives full and 



66 



^HOP SKETCHING 



complete information. Each detail has an appropriate legend, 
and the plate itself bears an appropriate title. 

Where a drawing is not intended for production work, but is 
merely for a single special job such as a machine repair or a part 




of a special machine, a freehand sketch may be made and used. 
The original sketch may be sent through the shop with the order, 
or it may be made on thin paper and a blueprint made from it 
and sent through with the order. Such drawings should never be 
destroyed, but should be labelled carefully and dated and filed 



ASSEMBLY AND DETAIL DRAWINGS 



67 



away, as the same repairs may be required again or another 
machine may be wanted at a future date. 

Fig. 85 shows a complete freehand sketch (assembly and 




S-R.H. SQUARE 

THDS. PER l" 



KNURLED. 



16 -THDS. PER r 



;/ SPRING, 3-C0ILS,**!0 B. fiiS-G. 
/i STEEL WIRE. ^"— i|^"x Zt' FREE 



^ STEEL WIRE, ^ 
-^ L-ENCBTH. 



"2-64- X I" RD. MD. SCREW. 



SLOTTED FOR 
SCREW DRIVER 

PIPE THREAD. 



HEX. 



Fig. 86. 



details) of a universal coupling. Such a coupHng is used to 
transmit power between two shafts which are set at an angle. 
The cast-iron cross-hatching is used throughout for all work in 
freehand sketching and the various materials are noted. The 



68 SHOP SKETCHING 

sketches, however, are complete and give sufficient information 
for the manufacture of the coupUng. 

PROBLEM 9A 

Fig. 86 shows a section assembly of an automatic grease cup. The 
pressure is applied to the plunger by a coiled spring, the motion of the 
plunger being regulated by the wing nut. Make an assembly drawing of 
the cup and detail drawings of the cup, plunger, cover, spring, and wing 
nut. Group them on the same sheet, if possible. 

PROBLEM 9B 

Make complete drawings, including assembly drawing with details of 
separate parts, of anj'^ one of the following or similar objects: 

Door hinge Hack saw frame 

Bicycle wrench Tap wrench 

Pipe cutter Machinist's clamp 

ASSIGNMENT 10 

48. Drafting-room Procedure. — When the design of a machine 
is first taken up in a drafting office, the chief engineer or a senior 
draftsman first makes a pencil-sketch assembly. He endeavors 
to provide for all clearances and to proportion the parts correctly. 
When a satisfactory sketch has been obtained, it is turned over 
to a competent draftsman to work up into a finished drawing. 
This finished assembly is often the result of careful and frequent 
consultation with the various other draftsmen and engineers, 
so as to have all the good ideas possible incorporated into the 
design. 

The draftsman who makes the assembly drawing decides what 
materials or metals it will be advisable to use in the several parts, 
what their treatment shall be, what proportions they shall have 
in order to give sufficient strength, etc. His drawing should 
show all general and vital dimensions and should be finished in 
such a manner that it may be placed in the hands of a junior 
draftsman or detailer to detail the various parts. Before going 
to the detailer, however, the assembly drawing should be sub- 
mitted to the chief draftsman and chief engineer for their 
approval. 

Under the supervision of the man who made the general 
assembl}^, the detailer then makes complete detail drawings of 
each piece of the machine. These, in similar manner, should 



ASSEMBLY AND DETAIL DRAWINGS 69 

also be submitted to the chief draftsman and chief engineer. 

In a large, well-regulated office, all these pencil drawings 
would then be turned over to the "tracer" who would trace them 
on tracing cloth. Tracing cloth is a tough, semi-transparent 
cloth which is placed over the pencil drawings. The. lines are 
then traced with black India ink, thus transferring the drawing 
to the cloth. These tracings should also be approved by the 
chief draftsman and chief engineer. In smaller offices all these 
operations might be performed by one man. 

The tracings are next properly indexed for filing away in the 
vaults. Thereafter, they may be issued on a check order system 
whenever it is desired to have blue prints made from them. 
Whenever radical changes are made in the construction of a 
machine, the old tracings are marked "obsolete" or "superseded," 
and are replaced in the current files by tracings of the new designs. 
If only one or two dimensions are to be altered, the old dimensions 
may be crossed out (not erased) and the new dimensions placed 
above or below the old ones. 

Blue prints are made on paper known as blue-print paper, 
which is sensitive to light. The tracing is placed over a sheet of 
blue-print paper in a printing frame, and then exposed to a 
strong light such as daylight or an electric light. This makes 
an impression on the blue print like the drawing on the tracing. 
It usually takes a minute or so to make the print in a fairly good 
light. The blue print is then removed and "fixed" in a water 
bath for a few minutes so that it will be permanent. The lines 
of the drawing then appear as white lines on a blue background. 
When blue prints are subjected to a great deal of hard usage in 
the shops it is well to mount them on some stiff cardboard or 
other firm backing and then to shellac or varnish the surface so 
as to protect them. 

PROBLEM 10 

Following carefully all directions given in preceding articles make comp- 
plete assembly and detail drawings of any one of the following or similar 
objects: 

Pipe vise Expansion arbor 

Boiler tube expander Inserted tooth-milling cutter 

Lathe or planer chuck Stilson or Trimo wrench 

Automobile engine circulating pump 



CHAPTER V 

GEARING 

ASSIGNMENT 11 

49. Spur Gears. — Spur gears are used for connecting parallel 
shafts and are, by far, the most common type of gears. Fig. 
87 A shows a pair of spur gears. If there is much difference in 
the sizes of a pair of gears, the smaller one is called the pinion and 
the larger one the gear. In a pair of gears, the one which drives 




SPUR C3EARS 

A 





RACK AND PINION 

B 



INTERNA.L OR ANNULAR GEAR 
AND PINION 

c 






BEVEL GEARS. 

D 



SPIRAL GEARS. 

E 

Fig. 87. 



NA/ORM GEARING 



the other is called the driver; the other one is called the driven 
gear or the follower. The change gears of a lathe are good exam- 
ples of spur gears. 

When a gear is used to drive a body in a straight line, a com- 



70 



GEARING 71 

bination known as a rack and pinion is used, as shown in Fig. S7B. 
These are sometimes seen on planer tables and on the spindle 
feeds of drill presses. The straight-line gear is called the rack, 
while the small gear is called the pinion. 

Occasionally a spur gear is used with teeth cut on the inside of 
its rim, as in Fig. 87 C. This is called an internal gear, an example 
of which may be seen on any lawn-mower. 

50. Bevel Gears. — When two shafts lie at an angle, so that 
their center lines would meet if extended, they may be connected 
by bevel gears. Bevel gears may usualty be found on drill- 
press drives and on the elevating screws for raising and lowering 
the cross rails of planers. 

The teeth of bevel gears taper toward the intersection of the 
center-lines of the shafts. 

When two bevel gears of equal size connect two shafts at 
right angles thej^ are called rniter gears. 

51. Spiral and Worm Gears. — When shafts lie at an angle and 
are also some distance apart they may be connected by spiral or 
worm gearing, as shown in Fig. 87 E and F. Worm gearing is 
used where a considerable reduction in speed is desired. 

52. Pitch Circles. — ^Let us suppose that we have two rolls or 
cjdinders as in Fig. 88, rolling together without slipping. In 





Fig. 88. Fig. 89. 

order to transmit more power than can be done b}^ the smooth 
rolling surfaces, projections are placed on B parallel to the axis, 
and corresponding recesses on A. If now we consider that A 
is provided ^\Tith similar projections and B with similar recesses, 
we can see clearly the direct development from the rolhng 
cylinders of Fig. 88 to the toothed cylinders of Fig. 89, and 
thence to the spur gears of Fig. 87 A. The circumferences of the 
cyUnders now become the pitch circles of the gears. Gear teeth 



72 



SHOP SKETCHING 



project part way beyond the pitch circles, but all calculations of 
relative speeds depend on the sizes of the pitch circles. 

53. Pitch Diameter. — The pitch diameter of a gear is the diam- 
eter at its pitch circle and is the diameter used in speed calcula- 
tions, sizes of teeth, etc. 

54. Pitch. — Pitch is a word used to indicate the size of teeth 
on a gear. There are two systems of denoting pitch. 

Diametral Pitch refers to the number of teeth on a gear for each 
inch of diameter of its pitch circle. For example, if there are 
32 teeth on a gear, and the diameter of its pitch circle is 4 in., 
then there are -t- = 8 teeth per inch of diameter of the pitch circle, 
or the diametral pitch is 8. 



ADDENDUM CIRCLE 



PITCH circle: 



DEDEMDUM ORCLE 
ROOT CIRCLE 




Fig. 90. 



Circular' Pitch is the distance between corresponding points of 
adjoining teeth measured on the pitch circle (see Fig. 90); for 
example, it is the distance from the center of one tooth to the 
center of the next, or from the side of one tooth to the corre- 
sponding side of the next, the distance, in both cases, being 
measured around on the arc of the pitch circle and not straight 
across. 

Circular pitch is a direct measure of the size of teeth; the 
greater the circular pitch the greater the size of tooth. Diametral 
pitch indicates the number of teeth for each inch of diameter and, 



GEARING 73 

therefore, the greater the number of the diametral pitch the 
smaller the size of tooth. Cut gears are almost always designed 
by the diametral pitch. Circular pitch is generally used in the 
design of cast gears so as to enable the patternmaker to space 
the tooth forms uniformly on the circumference of the rim. Any 
gear might, however, have been built according to either system. 
To determine which was used, it is necessary to measure or cal- 
culate the pitch according to both systems and see which comes 
out an even figure. 

55. Gear Calculations. — Circular pitch may be measured 
directly from one tooth to the next along the pitch line. It is 
more accurate, however, to measure the pitch diameter and count 
the teeth. 

The pitch diameter multiplied by 3.1416 will give the pitch 
circumference. 

The pitch circumference divided by the number of teeth will 
give the circular pitch. 

For finding the diametral pitch, the same items are noted; 
namely, pitch diameter and number of teeth. 

The number of teeth divided by the pitch diameter will give the 
diametral pitch. 

Example : 

What is the diametral pitch of gear having 48 teeth and a pitch diameter 
of 6 in.? 

Since the diametral pitch is the number of teeth per inch of diameter, for 
this gear it will be 48h-6=8 pitch, Answer. 

In calculating the pitch diameter of a proposed gear, having 
given the number of teeth and the diametral pitch, we divide 
the number of teeth by the diametral pitch. 

Example : 

What is the pitch diameter of a gear having 66 teeth of 12 diametral pitch? 
If there are to be 12 teeth per inch of diameter, the pitch diameter must 
be 66-^12 = 5^ in., ^nsiyer. 

To find the pitch diameter of a gear, having given the circular 
pitch and the number of teeth, multiply the circular pitch by 
the number of teeth ; this ^\ill give the pitch circumference ; then 
divide this by 3,1416 to get the pitch diameter. 



74 SHOP SKETCHING 

56. The Addendum. — This is the technical name given to 
that part of the gear tooth outside of the pitch circle. In the 
standard system of gearing in general use, the addendum is made 
equal to 1 divided by the diametral pitch. Thus, if a gear is 
8 pitch the addendum of the teeth is made | in. high. If a gear 
is 4 pitch, the addendum is i in. 

The outside diameter of a gear is calculated by adding twice 
the addendum to the pitch diameter. We have already found 
how to calculate the pitch diameter for a gear that is to have a 
given number of teeth of a given diametral pitch. 

_. ^ ^. Number of teeth N 

Pitch Diameter = 



The Addendum = 



The diametral pitch I 
1 1 



The diametral pitch P 
Adding twice the addendum to the pitch diameter, we get 

N 2 iV+2 
The Outside Diameter =p+p = — p — 

This may be stated in words as follows : 

To find the outside diameter of a gear, add 2 to the number of 
teeth and divide by the diametral pitch. This is the diameter to 
which a gear blank must be turned before the teeth are cut. 

Example : 

What should be the outside diameter for a 40-tooth gear of 10 pitch? 
40+2=42. 42^10=4:.2 in., Answer. 

57. The Dedendum. — This is the technical name for the work- 
ing depth of a tooth inside the pitch circle. It indicates the depth 
to which the teeth of one gear fit into the spaces of the other 
gear below the pitch circle and, therefore, for standard teeth, is 
the same distance inside the pitch circle that the addendum 
circle is outside the pitch circle. 

A certain amount of clearance is usually cut at the bottom of 
the spaces to allow for dirt and other foreign matter to work out 
of the gears without breaking the teeth. The amount of this 
clearance below the dedendum, or working depth circle, is usually 



GEARING 75 

made 0.157 divided by the diametral pitch. The circle at the 
base of the clearance is usually called the root circle. See Fig. 
90. The depth of a standard tooth is therefore 

Addendum H-Dedendum+ Clearance 
1 1 0.157 



pitch pitch pitch 

2.157 

pitch 

Example : 

To what depth should a 6-pitch tooth be cut? 
Depth = 2. 157-=- Pitch = 2. 157 ^6 =0.3595 in., Answer. 

58. Gear Repairs. — Gear repair jobs are common in a large 
industrial plant. The mechanic who can handle such jobs 
intelligently is therefore a valuable man. The student should 
familiarize himself with the names of the various gear parts 
shown in Fig. 90. 

When repairing a cut gear it is necessary to determine its dia- 
metral pitch and pitch diameter. The number of teeth on the 
gear should first be determined and then the outside diameter. 
We have shown that the outside diameter of a standard gear 

N-\-2 
is — p . This rule can be reversed to get the pitch from the out- 
side diameter. 

N+2 

The diametral pitch, P^JTJV^ ^^^^ ^^' ^^^ diametral pitch of 

a gear is obtained by adding 2 to the number of teeth and dividing 
by the outside diameter of the gear. 

The pitch diameter is then obtained by dividing the number of 
teeth by the pitch. 

The depth to cut a tooth is obtained by dividing 2.157 by the 
diametral pitch. 

Fig. 91 shows the necessary data to be given in ordering new 
gears from a maker. This gives complete information, and if 
carefully followed makes misfits almost an impossibility. 

59. Gear Drawings. — In detail drawings of gears, generally 
not more than three or four teeth are shown. Fig. 92 shows a 
typical working drawing of a spur gear. Notice that the 
number of teeth and the pitch are given in the title. 

The outside diameter and the pitch diameter are dimensioned 



76 



.S//OP SKETCHING 



DATA FOR ORDERING 
SPUR GEAR AND PINION 




Gear 



Pinion 



D 


d 


D 


d 


F 


f 


B 


b 



Number required 

Material 

Outside Diameter 

Pitch Diameter 

Face 

Bore 

Keyseat 

Number of Teetli 

„•, , (Diametral — 

P^^^^ {circular C 

Diameter of Hub H h 

Length Through Hub 1, 1 

Projections , P p 

Center Distance A 

When ordering Spur Gears to transmit a certain horse- 
power, do not fail to state number of revolutions, size of bores, 
and largest and smallest permissible diameters. 



FiCx. 91. 



GEARING 



77 



on the drawing. The depth of tooth is not always given, but 
may be dimensioned or given in a note if desired. 

In making a drawing of a cut gear it is necessary to calculate 
the circular pitch in order to lay out the few teeth to be shown. 
The circular pitch is obtained from the diametral pitch by divid- 
ing 3.1416 by the diametral pitch. Thus, the circular pitch for a 
gear of 4 diametral pitch is 3. 1416-^4 = 0.7854 in. The teeth and 




28 T, 4- R, Srur Gear. 

J-REQUIRED ' CAST IRON, 
SCALE : 3"= r. 



Fig. 92. 



spaces are each one-half of this in width on the pitch hne. A good 
looking representation of a tooth may be drawn with the compass 
by using the circular pitch as a radius and setting the center about 
half way between the pitch circle and the base circle. Draw the 
tooth outline in this manner and then round it shghtly into the 
base circle, freehand, instead of leaving the sharp corner. 

PROBLEM 11 

Make a working drawing of any cut spur gear to which you may have 
access. - 



CHAPTER VI 

ISOMETRIC DRAWING 

ASSIGNMENT 12 

60. Pictorial Drawing. — All the drawing work we have done 
so far has been straight mechanical projection. That is, we have 
shown only one side of-an obj ect in each separate view. It is often 
desirable, in making sketches or drawings, to show the entire 
object in one view. This is especially needed in the shop when we 
want to convey an idea of a desired object to a workman who is 




Fig. 93. 

unable to read and understand a regular mechanical ch-awing. 
Such a drawing must naturally give a more or less faithful 
picture of the subject and the name ''pictorial" drawing is used 
to describe it. There are several styles of pictorial drawing. 
The simplest for shop use is known as isometric drawing. 
9 79 



80 



SHOP SKETCHING 



Isometric drawing aims to give a picture of the object showing 
the three dimensions of length, breadth, and depth at equal 
angles with the eye. As we shall see, it is not exactly a true 
picture, as it takes no account of perspective. '^ Perspective" 
is the name we give to the apparent tapering of objects as they get 
more and more distant from the eye. A common example of 
perspective is a long straight line of railroad track whose rails seem 
to meet at a distant point. Isometric drawing does not allow 
for this perspective or foreshortening, but shows all parallel lines 
on an object drawn parallel on the paper and to their true length. 

61. Isometric Axes. — In isometric drawing we assume that we 
are looking toward one corner of an object, in such a manner that 




the three sides are shown in equal proportion. Then, in a rectan- 
gular figure, the three nearest edges would appear to run out 
from the corner at equal angles with each other. Fig. 93 shows a 
half size mechanical drawing of a plain rectangular block. In 
making a half size isometric drawing of it, as in Fig. 94, we would 
view the bar-from such a point that the three near edges ah, ac, 
and ad, would appear to make equal angles with each other. 
Their isometric projections would then be drawn as in Fig. 94 with 
the edges ah, ac, and ad meeting at angles of 120°. The same 



ISOMETRIC DRAWING 



81 



block could also be shown set upon end as in Fig. 95 by the 
same method. 

The three lines or directions are known as "isometric axes/' 
and in isometric drawing always intersect at angles of 120°. 
One axis is usually drawn on the vertical, while the other two are 
drawn at inclinations of 30° o.hove the horizontal. It is not 
necessary, however, that one should be drawn vertical so long as 
the lines make angles of 120° with each other. 




Fig. 95. 



Horizontal and cross dimensions in isometric are drawn at an 
angle of 30° above the horizontal; vertical dimensions are drawn 
vertical. All dimensions are usually laid out on these lines 
to their true length according to the scale desired. In reality, 
the lengths of these lines would appear shorter than they really are 
because they are sloping away from the eye. But we never bother 
about this, but simply lay them out to the true lengths. Draw- 
ings are thus laid out to different scales in isometric just as in 
regular mechanical drawing. 

6 



82 



SHOP SKETCHING 



62. Circles in Isometric. — If there are circles on any of the 
faces of an object, they will not appear as true circles in an isomet- 
ric drawing. As soon as we view a circle from an angle it appears 
to assume an oval or elliptical form. Figs. 97 and 99 show the 
form taken by a circle in isometric drawing and the method of 
constructing it is as follows : 



A 

i/ 


B 


1 V 

1 ^^^ 

D 


--^i 




Fig. 96. 



Fig. 97. 



Suppose we wish to represent a 1-in. circle on the top isometric 
plane; see Figs. 96 and 97. We first imagine that the circle is 
enclosed by a 1-in. square ABCD, Fig. 97, being sure to get the 
sides of this square parallel to the proper isometric axes. After 
the square is outlined, we draw the diagonals of this square, 
AC and BD. Then we connect the middle points of AB and 
BC with D, getting the lines MD and .YD. In the same manner. 





Fig. 98. 



Fig. 99. 



we join B with the middle points of the sides AD and DC, 
giving Hnes BO and BP. These lines cross the diagonal AC at 
points R and S, which are the centers for the short arcs at the 
ends of the ellipse, extending from M to P and from N to 0. We 
set the center point of the compass at R and with a radius equal 



ISOMETRIC DRAWING 



83 



to RM draw the arc MP. Then we do the same at S drawing NO. 
The centers for the long arcs are at B and D. With the compass 
point on D and a radius equal to DN, we connect M and N. 
With the same radius we then put the compass on B and connect 
P and 0. This gives us the complete isometric circle MNOP 
having four centers; namely, R, S, B, and D. 

The construction lines should be drawn in very lightly so that 
after the circle is drawn they can be erased easily, leaving only 
the circle. 

If a circle is to be shown on one of the side or end planes in- 
stead of on the top, the construction is exactly the same, except 











A 




B 


E 
F 










D 




c 






















Weidge 





Fig. 100. 



that the enclosing square is drawn with its sides running in dif- 
ferent directions, depending upon which face the circle is to be 
on. Figs. 98 and 99 show how a circle is constructed on the 
right-hand face of an isometric drawing. 

63. Oblique Surfaces in Isometric. — In making isometric draw- 
ings, we frequently encounter figures such as wedges, hexagons, 
etc., whose sides are neither parallel nor at right angles. These 
lines will not follow the usual isometric axes, but must have their 
angles determined by reference to some isometric axis. We will 
show this by making an isometric dra\ving of the wedge shown in 



84 



SHOP SKETCHING 



Fig. 100. Here we have the mechanical drawing of a wedge, 
and we wish to make the isometric. The side view consists 




Isometric View of Wedge. 
Fig. 101. 





Fig. 102. 



Fig. 103. 



entirely of lines at right angles or parallel to each other. The 
plan view, however, has lines which are not parallel, but that run 



I 



ISOMETRIC DRAWING 



85 



at smaller angles. To construct the isometric, we fi.rst enclose 
the plan in a rectangle ABCD. Then we lay off this rectangle 
on the isometric paper as shown by the broken lines in Fig. 101. 
Then we measure the distance AE in Fig. 100 and lay it off on 
the rectangle in Fig. 101. Next, we do the same with the dis- 
tance DF. By connecting E with B, and F with C in Fig. 101, we 
have the correct representation for the lines BE and CF. The 
other lines on the ends of the wedge can be drawn in the usual 
manner. The line along the lower edge is then drawn parallel 
to FC. After the drawing is completed, the construction lines 
for the rectangle ABCD can be erased, leaving the completed 
wedge. 




Fig. 104. 



If we wish to make an isometric drawing of a segment of a 
hex bar, we may proceed by the steps shown in Fig. 102 and 103. 
First, we make a mechanical drawing as shown in Fig. 102, and 
then draw a circumscribing rectangle about the hexagon of the 
upper plan view. Next, we draw this rectangle lightly in isomet- 
ric as shown in Fig. 103. We can then locate on this rec- 
tangle the corners of the hexagon, using the distances as meas- 
ured from the top view of the mechanical drawing. 



86 



SHOP SKETCHING 



64. Examples of Isometric Drawing. — Fig. 104 shows a mechan- 
ical drawing, and Fig. 105 an isometric drawing of a 2 in. XH in. 
Xi^ in. angle with rivet holes, drawn one-half size. It em- 
braces the principles of isometric drawing laid down in the 




Fig. 105. 

preceding articles and serves to show the adaptability of this 
method to simple cases. Note that all the lines of this isometric 
sketch are either vertical or make angles of 30° with the horizontal. 
In like manner the rivet holes, being circular, are laid out by 





first drawing circumscribing squares whose sides make angles of 
30° ^vith the horizontal. The method of constructing these rivet 
holes and the i%-in. fillet is shown in the enlarged views of Fig. 
106. Note that the holes appear different in the horizontal and 



ISOMETRIC DRAWING 



87 




Fig. 107. 




Fig. 108. 



88 



SHOP SKETCHING 



vertical parts of the angle iron, although the construction is the 
same. If the accurate curvature of the y^-iii- fillet or any other 
such arc is desired, we may determine it by the construction shown 
in the small sketch. Fig. lOQA. Consider the two isometric 
lines as parts of a square. We know that the arc will be tangent 
to the two isometric lines. Since the arc is one-fourth of a circle, 
we know that the two points of tangency will be mid-points on a 
f-in. isometric square constructed on these two isometric lines. 
Therefore, we lay off ab and ac equal to t^ in. At c and b, we 
draw bd and cd at right angles to the two lines ac and ab. From 











/^ 


^ 


1 






^ 


J) 


c 












T' 


1^ 

1 

1 


V 


I 
^ 






1 
1 
1 


' 


: 









Fig. 109. 



their point of intersection, d, as a center, we strike the arc with 
a radius db. 

Fig. 107 is a mechanical drawing and Fig. 108 is an isometric 
drawing of a bearing block. It shows all necessary construction 
lines, but these should not appear upon the finished drawing. 

Fig. 109 shows a mechanical drawing and Fig. 110 an isometric 
drawing of a square nut blank, with all construction lines. 
Notice how the champfer is provided for. 

65. Isometric Paper. — To do isometric drawing perfectly on 
plain paper requires the use of a T square and 30° triangle, 



ISOMETRIC DRAWING 



89 




Fig. 110. 



^|-o.,..^^^ 



■z^— ♦• 



5" 



lO' 






J-U 



-2t— 









T 

Jaw for I,0' Planer Chuck, 
j-required , mach. steel 
finish all over 
SCALE : 3"= r. 



3i" 






Fig. 111. 



90 



SHOP SKETCHING 



instruments which we do not have in this course. This can be 
avoided by making use of isometric sketching paper, such as 
shown on page 91. This paper is ruled to the correct 30° axes 
for this work, and you can lay down your dimensions directly 
on the ruled lines. Use the paper with its long dimension run- 
ning from left to right. 

PROBLEM 12A 

Make an isometric drawing of the planer chuck jaw shown in Fig. 111. 

PROBLEM 12B 

Make an isometric drawing of the cast-iron foundation washer shown in 
Fig. 112. 




-IflO 



:iT- 



't 



Foundation Wasmeir. 
i-required cast iron 

SCALE. 6"= l'. 



r 




Fig. 112. 



PROBLEM 12 C 

Isometric sketches should be made from some of the following or similar 
objects, using isometric paper: 



Steady rest guide 
Slotting tool 
Cutting off tool 



Solid steel wrench 
Tool post wrench 
Gib key 



ISOMETRIC DRAWINGS 



91 




92 



SHOP SKETCHING 



ASSIGNMENT 13 

66. Isometric Drawing on Plain Paper. — ^Ability to make 
good, clear isometric sketches or drawings with ease is the 
result of careful and conscientious practice. Therefore, it is to 
be hoped that the student will make many more isometrics than 
are actually called for in this work, in order to perfect himself. It 
is evident, of course, that ruled paper ^^'ill not always be available 
for working drawings. It then becomes necessary to use plain 
unruled paper, and to estimate the angles by the eye alone. 

After having made the drawings of the problems 12A, 12B, 
and 12C, on the ruled paper, the student should have a good clear 
idea of the proper locations of the isometric axes. In starting an 




Fig. 113. 



isometric sketch on plain paper it is best to first decide the proper 
place on the sheet for the near corner of the object. Through this 
point draw horizontal and vertical lines as showm in Fig. 113. 
Then, with the eye, divide each of the two right angles above the 
horizontal into three equal parts and thus locate the two other 
isometric axes at angles of 30° above the horizontal. These will 
help in estimating the proper angles and in keeping parallel 
lines, where such are required. Keep in mind the fact that it is 
only proper to lay down dimensions in the direction of the iso- 
metric axes, or center lines. Outline the general shape of the 
object and put in small details afterward. Too careful attention 
to minor lines in starting will often lead to distorted finished 
drawings. 



ISOMETRIC DRAWING 



93 



-IN 




U)|CO 

i_ 



I'drill 



4" DRILL 



"UieP^ 



InzT- 



fojco 



T 



Lever 

I- REQUIRED CAST IRON 
SCALE- 6"=r 




TT 

•OIOO 

_Jl 



Fig. 114. 




Offset Corner Brace 
i -required steel 
scale: 3"=i'. 



Fig. 115. 



94 SHOP SKETCHING 

Many of the circles and arcs for fillets, etc., can be drawn free- 
hand with a little practice and thus save considerable time in 
the making of isometric sketches. 

PROBLEM 13A 

Make a complete isometric drawing on plain, unruled paper of the cast- 
iron lever shown in Fig. 114. Draw the If-in. and 1-in. circles according to 
the method explained in Article 62, and then sketch in the f-in. and |-in. 
circles freehand, following the outlines of the large ones. 

PROBLEM 13B 

Make a dimensioned, isometric sketch of the offset corner brace shown in 
Fig. 115. The isometric sketch will show the shape of this brace very 
clearly to a workman who could not read the mechanical drawing of Fig. 
115. 



CHAPTER VII 

FREEHAND DRAWING 

ASSIGNMENT 14 

67. The Use of Sketching Paper. — While the student has used 
the rule and compass, in all drawings made so far, he will appre- 
ciate the fact that it is often necessary to make sketches freehand. 

The draftsman generally works up his preliminary rough drafts 
of drawings as freehand sketches which serve as a guide in making 
finished drawings. He usually keeps a sketch book in which he 
draws all sketches, and he learns by experience that it pays to 
make them neatly and to dimension them fully. Sketching paper 
with lines ruled both ways, to form squares, makes a very con- 
venient material for these sketches. Fig. 117 illustrates the use 
of this paper in freehand work. Quadrille ruled paper is excellent 
for the work as it has light-blue ruling both ways, forming |-in. 
squares on the paper. The lines on the paper will serve as a 
guide in drawing straight lines and in laying out circles. The 
divisions will also assist in laying out sketches to an approximate 
scale if desired. In all work in freehand sketching, the pencils 
should be kept well sharpened, so as to make clear, well defined 
lines, and the drawing should be kept as neat and clean as possible. 
The order of work for freehand sketching is the same as for mak- 
ing finished mechanical drawings with the aid of the drawing 
instruments. The center lines are first located. Then, usually, 
one view is sketched in completely and the others developed in 
their proper relations to it. 

The extension lines and dimension lines should all be drawn 
next, and the arrow heads put on all dimension lines, as in Fig. 
118. Then the piece may be measured up and the dimensions 
placed on the drawing. By this procedure, necessary dimensions 
are not so apt to be omitted. Suppose, for instance, that we wish 
to make a freehand sketch of the object shown in Fig. 116. 
Figures 117, 118, and 119 show the various stages of the work 
as just enumerated. A title is added to show the name of the 
object, the number required, and the material. 
10 95 



96 



SHOP SKETCHING 



Usually, in making freehand sketches, no attempt is made to 
draw the objects to scale, although the various parts of the draw- 
ing should bear the proper relative proportions to each other. 












. 








1 








1 


1 








1 








-^^ 


^h 


- 
















^fj^ 


^r 


















(C 


^^ 


















\\^JJ 
















r^^^ 


^/l^ 










1 






-^^ 


IS^ 










1 












■ 








































1 


' 1 ' 






i 










1 


1 \ 






1 










1 


11, 














1 


1 1 


1 1 












1 


1 \l 














1 1 


1 1 


1 ! ! ' 11 
















-^f 




1 

1 


1 













































































Fig. 116. 



Fig. 117. 













_lg JJ . 




t"^' ^^ 


— 






\\R-x}) \ 




~^ i<f ^ i" "'^ /r ^ 




W ^? 




i-^_j 








1 11 ■ ■ 




} } 








1 1 ' 1 1 




;t,i-&;l!!4-.«b k 




ai'ifNiiyl ^ — 
















Fig. 118. 



Fig. 119. 



Dimensions should always he given from center lines and finished 
surfaces. When a circle is to be drawn, the radius should be 
pointed off each way on the center lines from the point where the 
two center lines cross. Through the four points thus located, a 
circle may readily be passed freehand. Always put a complete 



FREEHAND DRAWING 



97 



title and the date on every sketch so that it can be identified at 
any later period. 

PROBLEM 14A 

Using ruled sketching paper, make freehand dimensioned sketches of the 
side and end views of the tool post shown in Fig. 120. 



W 



-JN 



16 f^ 



-J- 



ZV 



3lk 



41"- 



Toou Post. 

1 -REQUIRED MACh. STEEL. 
SCALE* 6"=l'. 




Fig. 120. 



PROBLEM 14B 

Make complete freehand dimensioned sketches of two objects— one from 
each of the following lists: 



Tool post wrench 

Socket wrench 

Milling machine crank wrench 

Lever for car pusher 

Cape chisel 



Lathe tool 

Steel mandrel 

Square center for lathe 

Wrecking bar 

Planer or shaper knife 



ASSIGNMENT 15 

68. Sketching on Plain Paper.— After having made sketches on 
ruled paper, the student should have a sufficiently clear idea of the 
difficulties and methods of freehand drawing to attempt the most 
common and useful form of freehand work; namely, sketches 
on plain unruled paper. 

7 



98 



SHOP SKETCHING 




DRILL. 



CoNKJECTiNG Rod 

FOR 



3x3' Two Cycle Engine 

l-REQUIRED BRONZE CASTING 
scale: 6= l'. 



Fig. 121. 



FREEHAND DRAWING 99 

In drawing a straight line, do not grip the pencil tightly nor 
endeavor to make the line with one slow continuous stroke. 
Rather make a series of short-strokes joined together. In draw- 
ing vertical lines, hold the hand to the right of the line so that 
the pencil swings freely up and down in the fingers while the hand 
rests firmly on the paper. Watch the edges of the paper to see 
that the long lines do not slant. Well laid out center-lines are of 
great assistance in keeping lines straight and parallel. 

PROBLEM 15A 

Make dimensioned, freehand sketches, on plain paper, of the views of 
the gas engine connecting rod shown in Fig. 121. 

PROBLEM 15B 

Sketch one object from the following list, or some similar object. 
Drill press table 
Steam engine slide valve 
Steam pump piston 
Gas engine cylinder head 
Milling machine over-arm 
Automobile steering wheel 

ASSIGNMENT 16 

69. Freehand Isometric Sketching. — Quite often isometric 
sketches have to be made freehand without the aid of ruler or 




Fig. 122. 



compass. In starting a freehand isometric sketch, locate the 
near corner of the object on the paper and sketch in the isometric 
axes through this point, as illustrated in Fig. 113. 

Circles in isometric may be drawn by an approximate freehand 



100 



SHOP SKETCHING 



method as follows. Sketch in lightly the circumscribing rect- 
angle. Locate the middle points of its four sides by the points 
e, f, g, and h; see Fig. 122. Next in order, draw the two long arcs 
gh and/e, and finally the two end arcs fg and eh to close the ends of 
the ellipse. This approximate method may be applied to the 
representation of circles in any plane. 

Dimension and extension lines should be drawn in the direc- 
tions of the isometric axes, as illustrated in Figs. 94, 95, 103 
and 105. 



PROBLEM 16 

Make complete isometric drawings, freehand, of any one article chosen 
from List A; and one from List B. Draw each on a separate sheet, and do 
not use a straight edge or compass. All work on these sketches is to be free- 
hand. Dimension yom* drawing, showing yom- dimension and extension 
lines extending in the direction of the isometric axes. 

List A 
Bench rammer 
Tool post 

Any blacksmith's tools (without handles) such as hardie, flatter, 
sledge, heading tool, swage, hot chisel, etc. 



Anvil 

Tool rest for lathe 

Bearing block 



List B 

Die block for press 

Ram for steam or drop hammer 

Over-arm for miller 



INDEX 



Acme threads, 32 
Addendum, 74 
Arrow heads, 7 

Assembly drawings in section, 56 
-and detail drawings, 63 

Bevel gears, 71 
Bolts, 33 

dimensions, table of, 34 

heads and nuts, 34, 35 
Broken lines, 13 

sections, 48 
Brown and Sharpe standard thread, 
32 

Cap screws, 40 
Circles in isometric, 82 

pitch, 71 
Circular pitch of gears, 72 
Compass, the, 20 
Conventions, thread, 36, 39 

cross-hatching, 58, 59 
for pencil work, 52 
Cross-hatching, 45 

conventions for, 58, 59 
for pencil work, 62 
Cross-sections, 45 

Dedendum, 74 
Detail sheets, 63 

Diameters of circles, dimensioning, 
22 

of screws and bolts, 31 
Diametral pitch, 72 
Dimensioning the drawing, 6 

circles, 22 

notes on, 26 
Dimension lines, 6 
Dimensions, arrangement of, 21 

of bolts and nuts, 34 
Don'ts for draftsmen, 28 
Drafting room procedure, 68 
Drawing from objects, 28 

to scale, 22 



Ellipse, construction of, 55 
Extension lines, 6 

Fillets, 25 
Finish, 22 

marks, 23 
Freehand drawing, 95 

isometric sketching, 99 

Gear calculations, 73 

drawings, 75 

repairs, 75 

teeth, representation of, 77 
Gears, data for ordering, 76 

kinds of, 70 
Gearing, 70 

HaK sections, 46 
Heads for bolts, 34, 35 

for screws, 40, 41, 42 
Hexagon, construction of, 27 
Hidden surfaces, 13 

Isometric axes, 80 
circles in, 82 
drawing, 79 

examples of, 86 

freehand, 99 

on plain paper, 92 
oblique surfaces in, 83 
paper, 88 

sample of, 91 
sketching, freehand, 99 

Lead of threads, 43 
Lettering, 8 
Lines, broken, 13 

dimension, 6 

extension, 6 

weights of, 21 

Machine screws, 41 
Making the drawing, 5 
Miter gears, 71 



101 



102 

Multiple threads, 43 



INDEX 



Nominal diameter of screws and 
bolts, 31 

Oblique surfaces in isometric, 83 
Order of procedure, 10 

Partial sections, 50 
Pictorial drawing, 79 
Pitch circles of gears, 71 

diameters of gears, 72 

of gears, 72 
circular, 72 
diametral, 72 

of threads, 33 
Principles of mechanical drawing, 1 
Projections, 1 

Relations between views, 4 
Revolved sections, 50 
Root diameter of screws and bolts, 
31 

Scales, 23 

Screws and screw fastenings, 31 

cap, 40 

machine, 41 

set, 41 
Sections, 45 

broken. 48 



Sections, half, 46 

partial, 50 

revolved, 50 
Set screws, 41 
Shortened views, 53 
Sketching, freehand, 95 
isometric, 99 

on plain paper, 97 

paper, use of, 95 
Spiral gears, 71 
Spur gears, 70 
Square threads, 32 

method of drawing, 39 

Tapped holes, 37 

Thread conventions, 36, 39 

Threads, depth of, 31 

forms of, 31, 32, 33 

multiple, 43 

right hand and left hand, 36 
Titles, 11 

U. S. Standard threads, 32 

Views, relation between, 4 

shortened, 53 
V threads, 31 

Whitworth threads, 33 
Worm gears, 71 
threads, 32 



NOV V6 1913 



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